Starting with the geometry and grinding wheel topography of the grinding wheel, the grinding force was studied in the mesoscopic and macroscopic angles, according to the change law of grinding force of45^#  steel. The relationships between the grinding depth, grinding speed and grinding force were obtained from the simulation of the grinding force in the mesoscopic point of view; a grinding nephogram on the base of grinding parameters and grinding force variation diagram from the simulation of grinding force in the macroscopic angle were obtained; the research on grinding force of mesoscopic and macroscopic angles were summed to obtain correction formula of grinding force of 45^#  steel.  The result of the simulation research and the grinding force correction formula showed： Grinding force with the grinding depth increased, and the larger grinding depth was, the more obvious grinding force variation tendency was; grinding force with the grinding speed decreased, when the grinding speed exceeded a certain rate of grinding, decreasing trend of grinding force slowed down.