The fracture of movable part is a serious issue in micro-electro-mechanical systems (MEMS) device application. However, its fracture mechanism is not clear yet. The fracture mechanism of movable part based on empirical electron theory (EET) of solids and molecules, in which fracture model is built based on valence electron structure and broken bond of the crystal plane is clarified. Simulation and test results match EET-fracture model quite well with low errors of 8.22 and 5.95%, respectively, which shows a good accuracy among existing fracture models. It is believed that EET-fracture model is quite effective and useful to evaluate movable part function in the research of MEMS devices.