The invention discloses a piston for a circular slider-crank mechanism, comprising a crown and a piston seat fixedly connected with the crown. The piston seat is provided with a circular slider accommodation hole. The edge of the end face of the circular slider accommodation hole and the region passing through the lumbar part of the piston seat are provided with reinforcing ribs which can be assembled on the piston seat in a dismountable manner. The lumbar part of the piston of the invention has higher strength or rigidity under the condition of increasing the volume or weight as little as possible. The invention also provides an internal combustion engine and a compressor. The lumbar parts of the pistons in the internal combustion engine and the compressor of the invention have higher strength or rigidity on the premise of increasing the reciprocating mass as little as possible.