UMo/Al fuel is a typical dispersion fuel and is becoming a focus of research in many countries as it has higher density, better thermal conductivity and stronger irradiation resistance. According to the structure characteristics of dispersion nuclear fuel, the periodic unit model is established and the mechanical behavior for UMo/Al dispersion fuel on different fuel volume and burnup is simulated by ANSYS software. The results show that maximum stress occurs in the middle of fuel plate. With the fuel volume fraction increasing, the risk of rupture of fuel plate corresponding increase. It reveal the mechanism of irradiation failure for dispersion fuel plate and the results can be demonstrated by the sample figure of irradiation.