Investment casting process is an important way to get complex parts of titanium alloy. However there are few research on the interfacial heat transfer coefficient (h) between casting and shell thus the temperature simulation of investment casting process of titanium alloy is often inaccurate. In order to get a relatively accurate h, a one-dimensional mathematical model for the reverse calculation of h between casting and shell in investment casting process of Ti6Al4V alloy was built and the analytic relationship between temperature and time/heat flux was established. Considering the calculated h is significantly affected by the error of parameters such as the specific heat capacity and thermal diffusivity of shell and position of thermocouples, research on the error of these parameters is essential. The relationship between the error of these parameters and the temperatures in the casting and shell was studied and it was found that the effect of different kind of error on the temperature field was obviously different. An experiment based on the one-dimensional mathematical model was done and temperatures of different positions were measured. Based on the effect of different kind of error and the difference between the calculate temperature field and the measured temperatures, the proportion of effect of each kind of error was assessed. These errors were revised on the basis of the assessment, thus a relatively accurate h between the casting and shell was obtained. The relationships between h and thickness of the solidified layer on the casting/temperature at the surface of casting can be divided into 4 stages: (1) Metal was liquid and h kept about 440 W/(m²K); (2) Solid layer appeared on the surface, and h declined nearly 60%; (3) Solid layer grew up before metal became completely solid and h declined nearly 20% of its maximum; (4) After metal solidified, h declined slowly as temperature on the surface of casting dropped. These relationships were applied in a three-dimensional model for numerical simulation of the temperature field. Temperatures of different positions in casting and shell were calculated and calculated temperatures agreed with measured ones well. Thus the accuracy of h was identified and it can help solve problems in the production in investment casting process of Ti6Al4V alloy.