This article has carried on the simulation research of tool wear in electrical discharge machining (EDM) small holes on titanium alloy with the finite element method. Aiming at electrode material removal process in EDM, a 3D thermodynamics model of single pulse discharge material removal is established with Ansys software. By simulating the Gaussian distribution of heat flux and thermal convection loads of discharge channel, the same type of surface heat source is exerted on both positive and negative electrodes with different distribution coefficients and different material characteristics, to analyze the surface temperature field in the region of tool and workpiece processing area, and respectively obtain the heat distribution law along the radius and depth directions of copper and titanium alloy electrodes, in the condition of small hole positive polarity EDM machining on TC4 with copper as the tool electrode. Using the birth and death element method, the volumes of material removal on both electrodes are calculated to analyze the tool wear. The experiments of small hole EDM machining on TC4 are carried out, and the results of simulation and experiment are compared. It is shown that the simulation model can not only accurately predict the relative wear of both electrodes, the simulation results of material removal volumes on both electrodes are also almost accurate.