Radiometer effect is a kind of thermal noise caused by temperature gradient. It is one of the main interfering factors to the inner-satellite, and is important to measure gravitational field. By analyzing the cause, the model of inner-satellite radiometer effect was established by the kinetic theory of gas molecules. In the model, the inner-satellite radiometer effect was divided into two parts. One was the reaction force and its torque caused by gas molecules which escaped from inner-satellite surface. The other was the force and its torque caused by collision of gas molecules which escaped from the cavity wall on the outer-satellite. Then the influence of various parameters to inner-satellite radiometer effect was analyzed and methods of reducing the inner-satellite radiometer effect were found. The results showed that through lowering the pressure and temperature gradient in cavity, as well as using materials with low surface-mass ratio, the acceleration caused by radiometer effect could be reduced.