The invention discloses a valve cover positioning and clamping mechanism for a solenoid valve cover thread testing machine, and the mechanism comprises a valve cover clamping device and a valve cover positioning device. The valve cover clamping device comprises a cylinder cushion block disposed on a first installation plane. A cylinder is disposed on the cylinder cushion block through a fixed angle bracket, and a piston rod of the cylinder is connected with a floating connector. The first installation plane is provided with a clamping fixing track, and the clamping fixing track is provided with a group of clamping and fixing sliding blocks in a matched manner. The clamping and fixing sliding blocks are disposed on a rack fixing plate, and the upper end face of the rack fixing plate is fixedly provided with a limiting block bar, an adjustment rack, and a floating connector connecting plate. The floating connector connecting plate is fixed with the other end of the floating connector. The first installation plane is provided with a screw fixing assembly. The mechanism can be used for replacing manual operation for the automatic detection of the thread of the valve cover, is high in efficiency, and is accurate in detection result. The mechanism reduces the manpower, and reduces the installation accidents.