A system for producing diesel fuel and jet fuel using Fischer-Tropsch synthetic oil, the system comprising a hydrofining reactor, a hot high-pressure separator, a first rectifying column, a hydrocracking reactor, a hydroisomerization reactor, a second rectifying column, a first mixing chamber and a second mixing chamber; wherein the hydrofining reactor comprises a raw material inlet and a hydrofining product outlet; the hot high-pressure separator comprises a separated oil outlet and a hydrofining product inlet which is connected to the hydrofining product outlet; the first rectifying column comprises a tail oil fraction outlet, a diesel fraction outlet and a separated oil inlet which is connected to the separated oil outlet; the first mixing chamber comprises a circulating hydrogen inlet, a first mixture outlet and a tail oil fraction inlet which is connected to the tail oil fraction outlet; the hydrocracking reactor comprises a hydrocracking product outlet and a first mixture inlet which is connected to the first mixture outlet; the second mixture chamber comprises a renewal hydrogen inlet, a second mixture outlet and a diesel fraction inlet connected to the diesel fraction outlet; the hydroisomerization reactor comprises a hydroisomerization product outlet and a second mixture inlet which connects with the second mixture outlet; and the second rectifying column comprises an aviation kerosene outlet, a diesel outlet and a hydrogenation product mixture inlet which is connected to hydrocracking product outlet and the hydroisomerization product outlet, and wherein the system further comprises a condensation fractionating column; the condensation fractionating column comprises a gas inlet, a fourth gas outlet and a liquid outlet; the hot high-pressure separator further comprises a first gas outlet; the first rectifying column further comprises a second gas outlet; the second rectifying column further comprises a third gas outlet; the first gas outlet of the hot high-pressure separator, the second gas outlet of the first rectifying column and the third gas outlet of the second rectifying column each connect to the gas inlet of the condensation fractionating column; the fourth gas outlet of the condensation fractionating column is connected to the raw material inlet of the hydrofining reactor; the second rectifying column further comprises a naphtha fraction outlet and a discharge pipe for cyclic utilization of the tail oil fraction and paraffin; the first rectifying column further comprises a naphtha fraction outlet; the discharge pipe of the tail oil fraction and paraffin is connected to the tail oil inlet of the first mixing chamber; the discharge pipe of the tail oil fraction and paraffin is connected to a paraffin outlet through a tee joint; and a pipe M between the fourth gas outlet and the raw material inlet of the hydrofining reactor is connected to an oil mixture inlet pipe and a circulating hydrogen inlet pipe. the hydrofining reactor comprises a raw material inlet and a hydrofining product outlet; the hot high-pressure separator comprises a separated oil outlet and a hydrofining product inlet which is connected to the hydrofining product outlet; the first rectifying column comprises a tail oil fraction outlet, a diesel fraction outlet and a separated oil inlet which is connected to the separated oil outlet; the first mixing chamber comprises a circulating hydrogen inlet, a first mixture outlet and a tail oil fraction inlet which is connected to the tail oil fraction outlet; the hydrocracking reactor comprises a hydrocracking product outlet and a first mixture inlet which is connected to the first mixture outlet; the second mixture chamber comprises a renewal hydrogen inlet, a second mixture outlet and a diesel fraction inlet connected to the diesel fraction outlet; the hydroisomerization reactor comprises a hydroisomerization product outlet and a second mixture inlet which connects with the second mixture outlet; and the second rectifying column comprises an aviation kerosene outlet, a diesel outlet and a hydrogenation product mixture inlet which is connected to hydrocracking product outlet and the hydroisomerization product outlet, and wherein the system further comprises a condensation fractionating column; the condensation fractionating column comprises a gas inlet, a fourth gas outlet and a liquid outlet; the hot high-pressure separator further comprises a first gas outlet; the first rectifying column further comprises a second gas outlet; the second rectifying column further comprises a third gas outlet; the first gas outlet of the hot high-pressure separator, the second gas outlet of the first rectifying column and the third gas outlet of the second rectifying column each connect to the gas inlet of the condensation fractionating column; the fourth gas outlet of the condensation fractionating column is connected to the raw material inlet of the hydrofining reactor; the second rectifying column further comprises a naphtha fraction outlet and a discharge pipe for cyclic utilization of the tail oil fraction and paraffin; the first rectifying column further comprises a naphtha fraction outlet; the discharge pipe of the tail oil fraction and paraffin is connected to the tail oil inlet of the first mixing chamber; the discharge pipe of the tail oil fraction and paraffin is connected to a paraffin outlet through a tee joint; and a pipe M between the fourth gas outlet and the raw material inlet of the hydrofining reactor is connected to an oil mixture inlet pipe and a circulating hydrogen inlet pipe.