Abstract: The reasons of end cracking and spalling of a 2510 steel plastic mould slider block were analyzed by means of macro analysis, hardness testing, chemical composition analysis, fracture analysis, metallographic examination and so on. The results show that white and bright deterioration layer produced at the thread surface during electric processing thread hole of the slider block. Because the deterioration layer was very brittle, micro cracks and spalling easily formed here and became the fatigue crack source. Under the action of alternating stress caused by the bolt spring, the cracks propagated outwards and extended along the concentric arc line around the thread hole, and finally resulted in the end cracking and spalling failure of the slider block. At the same time, the serious banded and network carbides reduced the material strength, which accelerated the fatigue cracking and spalling failure process of the slide block.