The invention provides a reciprocating sealed compressor, comprising a seal shell, a motor that is arranged in the sealed shell, a gas compressing device and an exhaust system, a cylinder block that fixes the motor, the gas compressing device and the exhaust system and connects the motor, the gas compressing device and the exhaust system with the sealed shell in an installation way by a spring; wherein, the gas compressing device comprises an air cylinder, a valve plate, a piston and a piston-rod, a cylinder head including a cylinder and a cylinder block connecting body. The compressor is characterized in that the exhaust system has a muffling structure with a tertiary expansion chamber; an air cylinder cover is a trilocular cylinder cover that is respectively provided with an induction chamber, an exhaust chamber and a primary expansion chamber which respectively form an induction cavity, an exhaust cavity and a primary expansion cavity after the trilocular cylinder cover is combined with the valve plate; a secondary expansion cavity is formed by a secondary expansion chamber arranged at the cylinder head and the valve plate; the tertiary expansion cavity is arranged on the cylinder block; the primary, secondary and tertiary expansion cavities are communicated mutually; the primary expansion cavity is communicated with the exhaust cavity; an exhaust pipe is communicated with the tertiary expansion cavity. The expansion cavity of the invention has the advantages that the muffling levels are numerous, the gas pulsation is small, the vibration noise of the compressor is low, and the production cost is low.