In recent years, WEDM has been adopted in precision machining as an important alternative machining method because of its greater flexibility and lower wear cost compared with traditional machining. Whereas wire breakage during WEDM is an unignorable problem that influences the machining quality and efficiency. Therefore, it has been a research topic of considerable interest. This work focuses on exploring the reason for the wire breakage. Firstly, by observing the wire after discharges and using the finite element method, a complete thermal model considering both latent heat and flushing efficiency was built. With this model the simulation of the crater on the wire was finished. Then based on the result gotten from the simulation and experiment, the inverse fitting was chosen to find the precise heat partition ratio to the wire. After that, a wire breakage experiment was done and through locating the position of discharges before wire breakage, the influence of consecutive discharges on the wire was simulated with the gotten model. Finally, the findings of this work allow for a more in-depth understanding of the effect of discharge accumulation on wire breakage.