The invention relates to a convenient to clamp automobile parts assembling and bolt screwing mechanism which comprises a gripper, wherein the gripper enables an air outlet pipe and a flange of an exhaust cylinder to be matched with each other and is matched with a screwing mechanism; the screwing mechanism comprises a tightening seat; a right movable seat and a left movable seat capable of movingleft and right are arranged on the tightening seat and are connected onto a movable air cylinder; flange bolt tightening devices matched with bolts are arranged on the right movable seat and the leftmovable seat; and the flange bolt tightening devices on the two movable seats are in one-to-one correspondence with bolt holes in the flanges in position and number. The invention aims to provide theconvenient to clamp automobile parts assembling and bolt screwing mechanism. The screwing mechanism matched with the gripper is arranged; the left and right movable seats are arranged on the screwingmechanism; the flange bolt tightening devices matched with the bolts are arranged on the left and right movable seats, and the flange bolt tightening devices are in one-to-one correspondence with boltholes in the flanges in position and number, so that the bolt screwing efficiency is greatly improved and the screwing man-hour is shortened.