The invention discloses an airborne gravity data downward continuation method and system combining ground gravity points. The airborne gravity data downward continuation method comprises the steps that aerial gravity data in an airborne gravity measurement system and ground gravity data in a ground gravity measurement system are obtained; aerial gravity measurement impact data are determined according to the ground gravity data; the aerial gravity data identical with the aerial gravity measurement impact data in the aerial gravity data are filtered, and the filtered aerial gravity data are determined; a point mass observation model is constructed according to the filtered aerial gravity data; the ground gravity data of a ground blank area are calculated according to the point mass observation model; and the ground gravity data of the ground blank area are evaluated, and ground gravity data of unmeasured ground gravity points are determined. By adopting the airborne gravity data downward continuation method and system, the evaluating precision of the ground gravity data of the unmeasured ground gravity points can be improved, and the calculation workload is decreased.