Natural gas accumulation sampling storage tank and accumulation sampling method thereof

The invention provides a natural gas accumulation sampling storage tank which comprises a storage tank body and a piston matched with the inner wall of the storage tank body, and the storage tank body comprises an upper cover plate, a cylinder body and a lower cover plate which are sequentially connected; the piston rod penetrates through the upper cover plate and enables the piston to move along the inner wall of the cylinder body; a pressure cavity is defined by the piston and the upper cover plate and used for introducing pressure gas and driving the piston to move. A sample cavity is defined by the piston and the lower cover plate and is used for storing a natural gas sample. Through the accumulation sampling storage tank, samples can be continuously collected, so that accumulated gas samples within a period of time are obtained. Besides, the cylinder body is divided into the pressure cavity and the sample cavity by the piston, and the piston is provided with a protection and test system, so that gas in t