To improve heat flux density at the exit of the integrator of arc lamp heat flux calibration system, an approach is proposed. Firstly, the principles and design objectives of the system are briefly introduced. Secondly, the selection and location of xenon arc lamp are analyzed. Thirdly, according to the restriction relationship among the lamp, the ellipsoidal specular and the integrator, relevant parameters of the ellipsoidal specular and the integrator are designed and optimized. Finally, a new calibration system with all optimum indicators is obtained. In the new calibration system, the heat flux density at the exit of integrator increases by 33% when unevenness is less than 3%. The truncation diameter and the depth of the ellipsoidal specular decrease by 16% and 18% respectively. Under the same process conditions, the results can lead to a higher process accuracy of ellipsoidal specular.