Abstract: Radiometer effect and outgas effect will occur in the vacuum chamber of the electrostatic accelerometer if temperature gradient noise exist.Based on kinetic theory of gases and statistical theory,the analysis and calculation show that the acceleration noise incluced by outgas effect is dozens of times larger than what radiometer effect incluced under the same condition,and the outgas effect also has greater influence on the sensitivity of the electrostatic accelerometer.Thus outgas effect should be an important reference factor for the design of the electrostatic acceler-ometer.