The present invention discloses an intermittently opened cracking crude oil apparatus comprising a high pressure container (1), a support post (2) and a gold sleeve (3). A sealed reaction chamber of natural gas (4) is formed between an exterior surface of the support post and an interior surface of the gold sleeve, and a sealed high pressure chamber (5) is formed between an interior surface of the high pressure container and an exterior surface of the gold sleeve. A gas outlet is provided in the support post and communicates the reaction chamber of natural gas, the gas outlet communicating a gas conduit (7), the gas conduit being connected to a natural gas collector (8). A movable valve needle (9) is provided on the gas outlet to control open and close of the gas outlet. A liquid inlet (10) is provided on the high pressure container and communicates the high pressure chamber, the liquid inlet communicating a liquid conduit (11) which communicates a high pressure liquid supply. A heater (12) and a nozzle of liquid nitrogen (13) are provided outside the high pressure container. A thermocouple (14) is provided on the high pressure container, the thermocouple being connected to a temperature control (15) which can control operating conditions of the heater and the nozzle of liquid nitrogen.