The invention relates to the technical field of thermostat, in particular to a thermostat shell assembly, an engine cooling system and a small circulation control method. The thermostat shell assemblycomprises a shell, a valve and a thermostat; the shell is provided with a first chamber and a second chamber; a communication cavity is arranged between the first chamber and the second chamber, andthe valve is arranged in the communication cavity and is used for connecting or disconnecting the small circulation of the cooling system; the first chamber is provided with a radiator water outlet; the second chamber is provided with a radiator water inlet; the thermostat is arranged in the first cavity and is used for opening or closing the radiator water outlet. The engine cooling system includes the thermostat shell assembly. The small circulation control method is characterized in that the method comprises the following steps of: setting the valve on the small circulation pipeline of theengine cooling system, and controlling the communication or disconnection of small circulation of the engine cooling system through the valve. By means of the valve, the communication or disconnectionof the pipeline of the small circulation is achieved, and the user experience is improved.