In　order　to　obtain　the　theoretical　displacement,　discharge　pressure　and　power　consumption　when　design　the　PC-type　single　screw　compressor　(SSC),　the　main　geometric　analysis　of　PC-type　SSC　has　been　carried　out　in　this　paper.　By　analyzing　the　intermeshing　area　formed　by　gate　rotor　tooth　and　groove　of　screw　rotor　and　centroid　distance,　the　mathematical　models　of　groove　volume　and　torque　were　presented　for　PC-type　SSC.　Analysis　of　a　typical　PC-type　SSC　with　117　mm　diameter　rotor　shows　that　the　calculated　entire　single　groove　volume　has　good　consistency　with　that　measured　by　3D　Pro/E　software,　with　percentage　error　about　3.771%,　the　periodic　variation　of　instantaneous　torque　is　the　same　for　different　inlet　pressure　levels,　the　torque　ratio,　with　its　value　close　to　1,　is　independent　of　the　inlet　pressure　of　SSC　and　that　the　power　consumption　increases　with　increase　of　inlet　pressure.　Results　from　the　established　mathematical　models　of　groove　volume　and　torque　is　of　great　importance　for　engineers　to　design　and　manufacture　the　PC-type　SSC.　©　2017,　Editorial　Department　of　Journal　of　Beijing　University　of　Technology.　All　right　reserved.