It is necessary for processing the ground tests from different types of aerial cameras to design a stewart platform with load adaptive capacity.Considering the range of cameras' weight and the electrical-mechanical structure of designed stewart platform,the relationship between the load(aerial camera) and the potentiometer(position feedback device) signal amplitude was studied.A measuring method for the inertia moment of the load automatically was presented using numerical calculation method.The method is simple and does not need to add any device to most digital control systems.The simulation experimental results show that R² is 0.997 3,RMS is 0.171 6 by 4th degree polynomial,while R² is 0.999 6,RMS is 0.063 78 by 5th degree polynomial.It comes out that the precision of 5th degree polynomial is coincident with the stewart platform.