The invention discloses a valve clack sphere grinding machine of a double eccentric semi-ball valve. A frame (1), a motor (2), a loading workpiece rotating main shaft (4) and a tool (5) are arranged on an engine base (3), wherein the frame is arranged on the upper part of the engine base and provided with an angle adjustment frame (6) with adjustable angles; a rotating auxiliary shaft (7) is fixedly connected to the angle adjustment shaft; a grinder clamping mechanism (8) is arranged on the rotating auxiliary shaft, and a semispherical grinder body (9) is fixedly connected to the grinder clamping mechanism; the lower part of the engine base corresponding to the rotating auxiliary shaft (7) is provided with the loading workpiece rotating main shaft which simultaneously rotates with the rotating auxiliary shaft and has opposite direction to the rotating auxiliary shaft, and the tool used for fixing a semi-sphere is arranged on the loading workpiece rotating main shaft; and the upper end of the tool is a semispherical positioning disk eccentrically arranged on the loading workpiece rotating main shaft. Through the adjustment of the angle adjustment frame, the grinder rotates on a semi-ball valve clack at a uniform speed so as to form mutually crossed reticular tracks and achieve an ideal ball grinding surface.