The present invention relates to dismounting free series cleaning method and apparatus of carbon dioxide ice, pulse circulation, vacuum ultrasonics and vapour, for engines. Said apparatus comprises an upper ultrasonic cleaning box connected with a spiracular atrium and a burning compartment of the engine, a lower ultrasonic cleaning crankcase oil tray connected with a crankshaft case, and a washer consisting of a carbon dioxide ice injection pump, a pulse diaphragm pump, a vacuum pump, a lotion vapour canister, a cog-wheel pump and a body case. The process for the apparatus is as follows: dismounting the valve bonnet, the carburettor or the electrical fuel oil injector, the sparking plug or the diesel oil injector; injecting, brushing and cleaning the machine members by using the carbon dioxide ice injection pump; connecting the ultrasonic cleaning box to the engine spiracular atrium, connecting the ultrasonic cleaning crankcase oil tray to the crankshaft case, and vacuum pumping the cleaning box, then executing the liquid-inletting pulse circulation cleaning under the function of the pumps; ultrasonic cleaning inside of the cylinder by ultrasonic cleaning the plates in the cleaning box and the cleaning crankcase oil tray; pumping back the cleaning agent; at the liquid-outlet, exchanging the cleaning agent and vapor tubes which are then dry-cleaned; reverting all the machine members; injecting new lubricant oil into the engine by using the cog-wheel pump.