Breakage is one of the important forms of tool failure.The traditional tool breakage analysis is mostly car- ried out through cutting test,which not only costs a lot but also lasts a long cycle.On the basis of peridynamic (PD) theory,this paper focuses on the micro breakage in the field near the main cutting edge in cutting process of 42CrMo large-diameter oil pipeline with cemented carbide tool.Firstly,finite element simulation of the cutting process is car- ried out to extract tool load.Secondly,in Visual Studio environment,the program for PD modeling and analysis is compiled by using C language according to PD theory.Then,with the help of image processing unit in Matlab,nu- merical analysis of micro breakage in the field near the main cutting edge of the cemented carbide tool is made in terms of the crack initiation position,the displacement trend of material particle in different directions and the growth trend of crack.The results show that the PD theory-based numerical analysis of cemented carbide tool’s mi- cro breakage helps reveal the mechanism and growth of micro breakage of the tool material in the field near the main cutting edge,that is,the micro breakage under certain working conditions is mainly caused by the shock load-in- duced micro cracks which is in a certain angle with the normal of rake face,and that the breakage trends to spread to the internal material discontinuously.