The invention discloses a semi-closed scroll compressor. The semi-closed scroll compressor comprises a machine shell, a head cover, a motor, a motor shaft, a scroll plate assembly and a bottom cover;a sealing plate is arranged above the scroll plate assembly, the head cover is located on the upper part of the machine shell, and a sealing cavity is formed between the head cover and the sealing plate; a safety valve is arranged on the head cover; a stepped cavity is formed in the head cover; an exhaust port is longitudinally formed in the center position of the top surface of the head cover, aninstallation cavity is longitudinally formed in the head cover, and a safety channel is transversely formed between the installation cavity and the exhaust port in a penetrating manner; the safety valve is located in the installation cavity; and the head cover comprises a fixed plate and a convex plate. The semi-closed scroll compressor has the advantages of being high in practicability and ingenious and reasonable in structural design; through improvement of head cover structure, the sealing cavity is formed between the head cover and the sealing plate directly, installation of a silencing cover is not needed, so that installation steps are simplified, and cost is saved; and meanwhile, the service life of the semi-closed scroll compressor can be prolonged through the design of the safetyvalve in the head cover.