Abstract: A calculation method of gravitational acceleration at any point on the earth was studied, and the research obtains the formula of gravitational acceleration considering the effects of the gravity of the earth，the sun and the moon，the height above sea level, the time of a year and a day. The acceleration component related to the sun’s gravity and the earth’s revolution acceleration takes the value of the variable sign in a day. The influence of the moon’s gravity is minor and the sign changes throughout the day. The study gives the maximum and minimum values of gravitational acceleration on the earth’s surface.

Key words: gravitational acceleration, sun's gravity, moon’s gravity, perihelion , aphelion