There　exist　some　input　errors　in　rehabilitation　training　of　rehabilitation　mechanism,　different　design　parameters　can　lead　to　different　errors　in　mechanism.　As　an　evaluation　index　of　mechanism　performances,　global　conditioning　index　did　the　analysis　work　of　mechanism　performances　through　defining　global　angular　velocity　precision　transmission　evaluation　index　and　global　torque　accuracy　transmission　evaluation　index.　According　to　3-RRS　mechanism　Kinematics　constraint,　it　solved　the　corresponding　Jacobian　matrix,　though　which　it　analyzed　the　performances　index　of　rehabilitation　mechanism　transmission　and　built　the　relations　of　every　design　parameter　and　performances　index.　In　addition,　it　is　verified　that　there　is　no　singular　posture　in　rehabilitation　exercising　of　mechanism　thus　can　meet　demands　of　ankle　rehabilitation.