Abstract: In response to the problem that C/SiC composite electrical discharge machining simulations commonly use a Gaussian heat source and ignore the thermal effect of the interstitial arc column, this paper performs a two-part equivalence with the thermal effect of the discharge process. Using an ellipsoidal heat source equivalent to an arc-arc column and a Gaussian surface heat source equivalent to the surface thermal effect of the workpiece, temperature field simulations are carried out in two directions, parallel and perpendicular to the carbon fibre, comparing a conventional Gaussian heat source with an equivalent heat source, and verified by experiment. The results show that: using the new equivalent heat source simulation, the size of the crater obtained is closer to the experimentally machined size than the conventional Gaussian heat source, with a 20% improvement in prediction accuracy.