The numerical simulation technology has been widely applied to industrial production and plays a great role in design of superplastic forming process and improvement of production quality. However, It must be point out there are more key problems to be improved in order to satisfied to requirements of real industrial superplastic forming process and to improve the accuracy of predicted results. A discussion on some key problems to be improved in numerical simulation of superplastic forming process is presented in this paper. These problems include: 1. Superplastic constitutive equations: Considering the different superplastic behaviors of various materials in industrial produce, the superplastic constitutive equations in the FEM simulation software should be include response of material superplasticity on different temperature and strain rate, grain size evolution during superplastic deformation under different deformation conditions and coupling relationship of macroscopic deformation and microstructure evolution. 2. Material parameter identification: Above supperplastic constitutive equations may be include more material parameters. How to precisely determine the material parameters, which are related to macroscopic deformation and microstructure evolution, is a problem to be solved. An inverse FEM method is proposed in this paper in order to solve the difficulty. 3. Fracture criterion: The blank fracture is a general forming defect in superplastic forming, therefore the prediction of material fracture is very important for design of superplastic forming process. However there is not the function in most numerical simulation software although the elongation data under different temperature and different strain rate have been obtained. The key is to establish a relationship between elongation and fracture criterion. In fact predicting other kind of forming defects (such as coarse grain and etc) is also very important. The key is also to establish the condition of starting the defect. 4. Other aspects of practical superplastic bulging: fraction force treatment, the part deformation during taking out the formed part from die. 5. Other aspects of practical superplastic bulk forming: If superplasticity of blank material is not so good due to coarse grain, one can control forming parameters so that grain refinement generates through dynamic recrystallization in the early forming period. In the last forming period, the blank has better superplasticity due to grain refinement that satisfies the need of forming complex shape parts.