The invention provides a bearing cover for a crank circular slider mechanism. The bearing cover is matched up with an engine body so as to form a complete engine body for supporting the crank circular slider mechanism; a cavity for the piston to do reciprocating motion is arranged on the bearing cover and runways are arranged on two sides of the cavity, and the runways are used for providing a guide track of the reciprocating motion for a guide track surface at the lower part of the piston of the crank circular slider mechanism. The bearing cover is capable of solving the problem of lower reciprocating motion guidance of the piston movement, so that the reciprocating motion of the piston is stably continued. The invention simultaneously provides an internal-combustion engine and a compressor by using the bearing cover.