Abstract: On the lunar surface, the gravity is only 1/6g while it is 1g on the earth surface. Investigating the effects of gravity has great significance to the optimization of excavator designed for lunar excavation. DEM is employed to simulate excavation tests with different excavation depths and gravity fields. The effects of gravity on excavation force, energy consumption and sliding surface are studied. Then the relation among excavation force, depth and gravity is fitted. The results show that the excavation force and energy consumption increase with the gravity while the range of affected area decreases. The excavation force increases with depth.