The amount of helium used in a balloon is an important issue, which directly affects balloon′s ascent velocity and altitude, and then affects the reliability and stability of the platform. Therefore, the study of accurate calculation method of helium is requested. Vertical dynamic model of balloons was established and the theoretical values of initial ascent velocity were calculated. It can be used to compare with the actual initial ascent velocity and provide a basis for evaluating helium inflation calculation methods. Three helium inflation calculation methods of high-altitude balloon were summarized, the accuracy and error range of the three methods were analyzed and compared according to the flight experiments. The buoyancy compensation law was put forward, and three methods have been evaluated. Through the study, it shows that the existing helium inflation calculation methods can be modified effectively, and then it can provide guidance for future flight experiments.