Based on the achievements of early works, a volumetric error modeling flow which is based on multi-body system theory is put forward. The flow includes 4 key steps mainly: describing structure, setting up coordinate system, creating characteristic matrix and generating volumetric error model are respectively. The operating method of every step is discussed in detail and the solving formula is given. At last, taking the VMC650 machining center of milling and boring which is developed by a machine tool factory as example, the validity of modeling flow is verified. This study can be used as a reference for opening automatic modeling system.