To improve on the lamp source set of the system for the heat flux sensor calibration, the simulation study is implemented in the paper. Based on the luminance distribution, the composition of xenon short arc lamp is designed and its power distribution is calculated. The angle distribution is simulated by angular apodization files. Then the model of the lamp source set is built and the radiation on the exit of the integrator is calculated. Compared with the test result, the average radiation on the exit of the integrator in test deduces about 49% and the loss of radiation increases with the increasement of the caliber of the integrator. By theoretical analyzing and experimental verifying, the loss of radiation is because the collection efficiency of the ellipsoidal specular reflector falls by 40% in test. And the reason why the loss increases with caliber of integrator is that the xenon short arc lamp model in this paper reflects well the feature that the density of the power of xenon short arc lamp descends from the cathode to the anode.