The invention relates to an analyzing and modelling method of milling force of a flat spiral end milling cutter. According to the method, workpiece material characteristics, cutter geometry, cutting conditions and milling modes serve as model input parameters, consideration is given to the influence on the cutting force by a cutter cutting edge radius, a variable sliding friction coefficient and cutter bounce, shear flow stress is calculated through a Johnson-Cook constitutive model in a model, each cutting edge of the milling cutter is scattered into multiple microelements in the cutter axis direction, the cutting characteristic of each microelement is equivalent to an inclined cutting process, cutting force exerted on each cutting microelement is obtained through an analytical model of inclined cutting force, then cutting force of all the cutting microelement is superposed, and a milling force value of the milling cutter is obtained. According to the analyzing and modelling method of the milling force of the flat spiral end milling cutter, cutting mechanism, relevant stress, strain and a strain rate in the cutting process and the distribution situation of the temperature can be reflected truly, the milling force can be quickly predicted only by inputting the cutting conditions and workpiece characteristic parameters, and the method is high in accuracy and rapidity.