A threedimensional heat transfer model of the noncontact split mechanical seal was established to study the deformation law of split mechanical seal.The frictional heat,heat partition coefficient and the convective heat transfer coefficient were calculated,the influences of shaft speed and flushing on steadystate temperature field,thermal deformation and thermalstructural coupled deformation of the split mechanical seal were analyzed,and the effect of clamping pressure on thermalstructural coupled deformation was studied.The results show that the highest temperature is located on the inner diameter of the seal end face,and the temperature of the seal end face of split stationary ring is significantly higher than that of the split rotating ring.The positive coning deformation of the seal end face and parting surface is generated by temperature field,however,the deformation can be effectively suppressed by clamping pressure.When the shaft speed is increased,the positive coning deformation of the seal face and parting surface of split rotating and stationary rings is increased,and the thermalstructural coupling deformation of seal face is also increased.When the flushing is intensified,the thermal and thermalstructural positive coning deformation of seal face and parting surface of split rotating ring is decreased,while the deformation of split stationary ring is increased.When the clamping pressure is increased,the thermalstructural coupling deformation of split rotating and stationary rings is increased.