The invention discloses a bottle cap. An outflow channel, a valve body, a valve part, a power part, an elastic diaphragm are arranged on the bottle cap; a liquid outlet is formed in the valve body; a liquid can flow out from the liquid outlet; the valve part can open or close the liquid outlet; the power part can control the valve part to move; the elastic diaphragm can isolate the outflow channel from the power part; one end of the elastic diaphragm is immovably and fixedly connected with the valve body; the other end of the elastic diaphragm is fixedly connected with a driving mechanism and can perform reciprocating motion with the driving mechanism. The bottle cap provided by the invention is simple and compact in structure and convenient to use, and the parts are not liable to be corroded so that the bottle cap has a long service life.