The invention discloses a horizontal rotating two-stage enthalpy increasing compressor. The compressor comprises a casing (1) as well as an upper flange (2), an upper gas cylinder (3), a separating plate (4), a lower gas cylinder (5), a lower flange (6) and a lower cover plate (7) which can be arranged in the casing (1) in the axial direction of the casing (1); the lower flange (6) comprises a medium pressure cavity (8) communicating with a gas inlet of the lower gas cylinder (5); through holes (9) for communicating the medium pressure cavity (8) with a compression cavity of the upper gas cylinder (3) are correspondingly formed in the separating plate (4), the lower gas cylinder (5), the lower flange (6) and the lower cover plate (7); and a gas replenishing and enthalpy increasing port (10) communicating with the medium pressure cavity (8) is further formed in the casing (1). With the compressor, the inside temperature of a pump body can be reduced, and the compression efficiency of the compressor can be improved.