Abstract: Jetting trenching has been widely used in submarine pipeline laying. In order to improve the understanding on jetting trenching in stiff clay, a physical model test system that could be used for jetting trenching in stiff clay was designed. Stationary and moving jetting tests under submerged conditions were conducted, and the effects of initial jetting velocity, of jetting time, of target distance, of soil strength, and of nozzle moving speed on the jetting results were analyzed. The test results show that: in the stationary jet tests, under the constant soil strength and target distance, the jetting depth increases linearly with the increase of initial jetting velocity, and the normalized jetting depth was proposed to remove the influence of different factors; and in the moving jetting tests, when soil strength, nozzle moving velocity, and target distance remain constant, the jetting depth also increases linearly with increase of initial jetting velocity. And the relationship between normalized trench depth and initial jetting velocity was established. Based on the principle of equal jetting depth, an equation that connect the stationary jetting test to the moving jetting test was constructed, and the jetting depth in moving jetting test can be inferred through stationary jet experiments conducted under identical experimental conditions. In addition, the critical jetting velocity was derived upon the results of the stationary jetting test, and the relationship between the critical jetting velocity and soil strength was established. According to the bearing capacity theory, the bearing capacity factors in the stationary and moving jetting tests were obtained. The findings of this study can provide valuable references for jetting trenching in stiff cohesive seabed.