The invention discloses a check valve which comprises an upper valve body and a lower valve body. The lower valve body is connected with the upper valve body, a cylindrical upper valve cavity is arranged on the central axis of the upper valve body, a lower valve cavity is formed by the lower valve body and the bottom of the upper valve body in an enclosed manner, a valve spool seat is arranged in the lower valve cavity, a valve spool is inserted in the valve spool seat, a conical opening is formed in the bottom of the upper valve cavity, the valve spool comprises a circular truncated cone matched with the conical opening of the upper valve cavity, a cylindrical head is arranged on the top of the circular truncated cone and is matched with a cylindrical cavity at the rear of the conical opening of the upper valve cavity, a stepped shaft is arranged at the lower end of the valve spool, the lower end of the stepped shaft is inserted into the valve spool seat, and a spring is arranged between the stepped shaft and the valve spool seat. Compared with an existing check valve with a valve spool abutted to a cavity, the check valve has the advantages that a cavity is of a cylindrical structure with the conical opening, the circular truncated cone which is matched with the conical opening is arranged at a seal end of the valve spool, and the cylindrical head is arranged on the top of the valve spool, so that the valve spool can be deeply arranged in the cavity when sealed, and a reliable sealed structure can be formed.