Aiming at the design selection and commissioning process, the concept and parameter of balance force fluctuation and volatility were put forward. The balance requirements, types and characteristics of the balance system were discussed for vertical components of CNC machine tool, the balance characteristics of self-circulation hydraulic balance system and the internal relationship of each link were mainly analyzed. Taking the requirements of balance terminal parameters, balance force and its fluctuation as input variables, the complete parameter calculation formula of self-circulation hydraulic balance system meeting the vertical balance characteristics and requirements of CNC machine tool was deduced, and the parameter influence relationship, the specification determination method and installation and connection requirements for the accumulator were discussed. After practical application and verification, the analysis, calculation and selection methods are correct and effective.