The thermal load and heat transfer performance of heavy vertical lathe rotary table was numerically investigated by adopting fluid solid interaction (FSI) method which makes external boundary conditions into internal. Flow field of air and temperature distributions of workbench, base and hydrostatic oil film were presented in the velocity range of 5~50r/min. The simulation results show that the velocity rising not only causes temperature of oil film increasing significantly, but also causes its carrying capacity decreased. What’s more, the velocity rising strengthens the convection of cooling surfaces and the heat dissipation of base is undervalued above 25r/min, so the temperature of cooling surface is not significantly increased which aggravates heat concentration. FSI method turns the external heat transfer boundary conditions into internal boundary conditions, which makes the simulation more close to actual situation. Meanwhile, numerical simulation results are consistent with the results of infrared thermal imager temperature measurement, which validate the numerical simulation, expand the application domain of FSI method, also lead lathe cooling situation analysis more reliable and accurate.