The invention relates to a water meter injection molding process. An injection molding machine, an upper mold base and a lower mold base are included, the injection end of the injection molding machine is fixedly connected with the upper mold base, and a mold locking part of the injection molding machine is fixedly connected with the lower mold base. The lower mold base comprises a movable mold base plate, a supporting plate, an ejector rod fixing plate, an ejector rod base plate, a large ejector rod, a movable mold plate, a concave mold plate, a lateral mold core, a positioning frame and a guide column, liquid plastic is introduced into a gap between a convex mold plate and a convex mold block through the upper mold base, and meanwhile the size of the upper side of a plastic part needingto be machined is limited. The upper mold base and the lower mold base are aligned and positioned,the plastic part obtained after injection molding is completed is pushed out through the lower mold base, the size of the lower side of the plastic part is limited, meanwhile, horizontal displacement of the lateral mold core is controlled, and the concave mold plate and the convex mold plate are further aligned.