The anti-sliding capacity is an important problem. Therefore, the model tests are used to study the mechanism of anti-sliding stability of gravity anchor under the combined loading in the sea. The results of tests show that, when a gravity anchor is used as a temporary anchorage foundation of a ship, the sliding of a gravity anchor is determined by its displacements. Based on the sliding mechanism, the slice method is proposed to analyze the anti-sliding stability of the gravity anchor. The lateral bearing capacity is calculated and compared to that obtained by the method often used and the results show that it increases about 17% which is more close to the results of model tests.