In the floor radiant heat flux materials testing device，in order to study the issue of calibration datapoint curve model is set up． Using cubic spline interpolation to curve fitting，the radiation heat flux distribution curve is established，and compared with the traditional least squares fitting has a higher accuracy，more suitable foractual application． using VB and Matlab mixed programming technology，to implement in the PC test software． Inthe fire test，this can accurately calculate the radiative heat flux of floor materials． The method has been applied in the actual test system，the practical popularize value．