A control parameter optimizing system comprising: an objective function setting section that is adapted to set an objective function to be optimized in controlling an operation of an existing power plant; a plant model that is adapted to simulate the operation of the existing power plant and calculate a process amount of the plant and a value of the objective function; a control parameter optimizing section that is adapted to optimize values of control parameters of the existing power plant using the plant model in such a manner as to optimize the objective function; a control parameter setting section that is adapted to extract control parameters from a control parameter information of the existing power plant and set the extracted control parameters to a control model in the plant model; a physical parameter setting section that is adapted to extract physical parameters from a plant characteristic information of the existing power plant and set the extracted physical parameters to a physical model in the plant model; and a design parameter setting section that is adapted to extract design parameters from a plant design information of the existing power plant and set the extracted design parameters to the physical model, wherein the control parameter optimizing section includes: an optimization control parameter selecting section that is adapted to select, based on control logic information extracted from a control logic database of the existing power plant, a control parameter from the control parameters as an optimization control parameter that is for use in optimizing the objective function; and an optimization control parameter adjusting section that is adapted to adjust the value of the optimization control parameter using the plant model in such a manner as to optimize the objective function, characterized in that the objective function is a start-up time, a rate of load change, an equipment lifetime consumption, a fuel cost, or a generation efficiency, which is defined by a function of a plant process amount, and the control logic information is made up of control logic modules interconnected hierarchically via signal lines, and the optimization control parameter selecting section is adapted to extract, as related control parameters, control parameters related to the objective function by detecting control parameters connected to a signal corresponding to the objective function in a hierarchically retroactive manner on the low-order side of the control logic modules, and select the optimization control parameters from the related control parameters. an objective function setting section that is adapted to set an objective function to be optimized in controlling an operation of an existing power plant; a plant model that is adapted to simulate the operation of the existing power plant and calculate a process amount of the plant and a value of the objective function; a control parameter optimizing section that is adapted to optimize values of control parameters of the existing power plant using the plant model in such a manner as to optimize the objective function; a control parameter setting section that is adapted to extract control parameters from a control parameter information of the existing power plant and set the extracted control parameters to a control model in the plant model; a physical parameter setting section that is adapted to extract physical parameters from a plant characteristic information of the existing power plant and set the extracted physical parameters to a physical model in the plant model; and a design parameter setting section that is adapted to extract design parameters from a plant design information of the existing power plant and set the extracted design parameters to the physical model, wherein the control parameter optimizing section includes: an optimization control parameter selecting section that is adapted to select, based on control logic information extracted from a control logic database of the existing power plant, a control parameter from the control parameters as an optimization control parameter that is for use in optimizing the objective function; and an optimization control parameter adjusting section that is adapted to adjust the value of the optimization control parameter using the plant model in such a manner as to optimize the objective function, an optimization control parameter selecting section that is adapted to select, based on control logic information extracted from a control logic database of the existing power plant, a control parameter from the control parameters as an optimization control parameter that is for use in optimizing the objective function; and an optimization control parameter adjusting section that is adapted to adjust the value of the optimization control parameter using the plant model in such a manner as to optimize the objective function, characterized in that the objective function is a start-up time, a rate of load change, an equipment lifetime consumption, a fuel cost, or a generation efficiency, which is defined by a function of a plant process amount, and the control logic information is made up of control logic modules interconnected hierarchically via signal lines, and the optimization control parameter selecting section is adapted to extract, as related control parameters, control parameters related to the objective function by detecting control parameters connected to a signal corresponding to the objective function in a hierarchically retroactive manner on the low-order side of the control logic modules, and select the optimization control parameters from the related control parameters.