The work aims to establish a parison dimension prediction method based on finite element analogy in view of the complexity of the wall thickness control. Numerical simulation of parison inflation was analyzed by software Workbench-POLYFLOW. The wall thickness distribution was obtained in the condition of uniform parison dimension. The effect of initial parison dimension on the final wall thickness distribution was analyzed. The IBC tank thin part and its corresponding parison position were located. The initial thickness of parison axial control points was adjusted to get the initial thickness curve in parison axis direction. The simulation results showed that the range of thickness was 2.27 mm. Empirical curve of parison was determined by trial production of large blow molding machine. The result verified the reliability of the method. In conclusion, the prediction method has short production cycle, high accuracy and good practical value.