Abstract: Based on the thermal-hydraulic system analysis code RELAP/SCDAPSIM, the models of the primary loop and secondary loop and the safety injection system of the small offshore reactor are built, and LOCA with a double ended break under different inclination angles are simulated. Simulation results show that, longitudinal inclination has little effect on thermal parameters of the reactor, while lateral inclination does have a significant influence, and steep edge effect exists. Particularly, when the lateral inclining with large angle occurs, there is a significant reduction of core water level due to the redistribution of liquid coolant in the primary loop, and peak cladding temperature of the fuel is raised about 520℃.