In　the　single　screw　refrigeration　compressor　(SSRC),　the　single　slide　valve　capacity　control　mechanism　(SVCCM)　is　the　functional　component　used　to　achieve　capacity　control　under　different　load　conditions　with　cooperation　of　screw　rotor　and　housing.　In　this　paper,　a　new　calculation　model　considering　internal　compression　and　leakage　is　presented　to　research　the　capacity　control　process　and　built-in　volume　ratio　control　process.　By　this　model,　the　actual　capacity　and　built-in　volume　ratio　at　different　slide　valve　work　locations　can　be　determined　using　the　calculated　by-pass　area　and　discharge　area.　The　influences　of　structural　parameters　of　the　slide　valve　to　the　control　characteristics　of　the　capacity　control　process　and　the　thermodynamic　properties　of　the　compressor　are　analyzed.　Through　the　comparison　of　the　capacity　control　process　and　the　built-in　volume　ratio　control　process,　the　axial　displacements　of　the　slide　valve　required　in　the　capacity　control　and　in　the　built-in　volume　ratio　control　were　obtained.　All　of　this　work　can　provide　the　basis　for　the　later　optimization　design　for　the　slide　valve.