The differential temperature heat treatment process provides a new way for the forming and manufacturing dual-performance blisk of titanium alloy. A stable and controllable gradient temperature field is the key to obtain a gradual gradient microstructure in the transitional zone of the blisk. This article established a finite element numerical simulation model of the temperature field in the transition zone of Ti6242S titanium alloy bar during differential temperature heat treatment based on the comprehensive heat transfer coefficient at different temperatures of Ti6242S titanium alloy. The effects of process parameters on temperature field are revealed. It is found that the larger the temperature difference between high and low temperature zone is,the larger the temperature difference in transitional zone is. Reducing the diameter of the bar results in an increase of the temperature gradient in the transition zone, and the temperature difference in the transition zone increases as the width of the insulation plate increases. Meanwhile, holding time have no significant effect on temperature field in transitional zone. The temperature at the midpoint of the transition zone is slightly higher than the average of the highest and lowest temperatures in the transition zone, which is caused by the change of the thermal conductivity and heat transfer coefficient with temperature. Due to the obstruction of the insulation board, the bar near the insulation board receives and emits less heat radiation, resulting in a wider gradient temperature field than the width of insulation board.