A method (100, 200) for an X-ray-based calibration and adjustment of axis systems by means of an X-ray system comprising a radiation source and a radiation detector, wherein the X-ray system includes two multi-element robots; wherein a first one of the two robots moves the radiation source, and a second one of the two robots moves the radiation detector, so that the radiation source and/or the radiation detector are movable in dependence on machine parameters for driving the robot, comprising: establishing a kinematic model of the X-ray system with all the kinematic relations for a first position (51t1) on the movement trajectory and describing the same using a first set of kinematic parameters and using parameters to be calibrated, wherein the first set of kinematic parameters and the parameters to be calibrated define a first equation of a system of equations; setting the starting values for the parameters to be calibrated; and calibrating comprising: establishing an X-ray projection of a calibration body for the first position (51t1) on the movement trajectory in order to acquire a first measuring result for at least one feature of the calibration body; and comparing the first measuring result to a respective reference in order to determine an error measure; and solving the system of equations in order to determine the parameters to be calibrated; wherein the parameters to be calibrated describe an offset of the radiation source relative to the robot, described in the kinematic model, which moves the radiation source; and/or wherein the parameters to be calibrated describe an offset between the X-ray detector and the kinematic model of the robot which moves the radiation detector. establishing a kinematic model of the X-ray system with all the kinematic relations for a first position (51t1) on the movement trajectory and describing the same using a first set of kinematic parameters and using parameters to be calibrated, wherein the first set of kinematic parameters and the parameters to be calibrated define a first equation of a system of equations; setting the starting values for the parameters to be calibrated; and calibrating comprising: establishing an X-ray projection of a calibration body for the first position (51t1) on the movement trajectory in order to acquire a first measuring result for at least one feature of the calibration body; and comparing the first measuring result to a respective reference in order to determine an error measure; and solving the system of equations in order to determine the parameters to be calibrated; establishing an X-ray projection of a calibration body for the first position (51t1) on the movement trajectory in order to acquire a first measuring result for at least one feature of the calibration body; and comparing the first measuring result to a respective reference in order to determine an error measure; and solving the system of equations in order to determine the parameters to be calibrated; wherein the parameters to be calibrated describe an offset of the radiation source relative to the robot, described in the kinematic model, which moves the radiation source; and/or wherein the parameters to be calibrated describe an offset between the X-ray detector and the kinematic model of the robot which moves the radiation detector.