Analyzing　of　nonlinear　carrying　performance　of　hydrostatic　ram　is　among　key　research　questions　to　improve　heavy　machine　tools　because　the　machining　precision　will　be　directly　influenced　by　it.　A　dynamic　model　of　nonlinear　supporting　characters　for　hydrostatic　ram　is　developed　in　this　work.　Modified　Reynolds　equation　is　resolved　by　finite　difference　method　numerically　to　determine　the　carrying　capability.　Dynamic　equilibrium　equation　of　hydrostatic　ram　under　cutting　force　impact　is　solved　by　Runge-Kutta　method　to　obtain　the　variation　of　tool　tip　position　and　evaluate　the　machining　accuracy.　An　optimal　oil　supply　rate　allocation　and　oil　pad　size　is　proposed　to　improve　the　static　and　dynamic　performance　simultaneously　based　on　method　of　bisection.