In recent years, with the implementation of the concept of environmental protection and the needs of urban water resources protection, many areas have restricted the pumping of groundwater, resulting in a large number of foundation pit projects must find new ways to stop water. In this regard, a new foundation pit supporting method " underground diaphragm wall + horizontal frozen back cover " is proposed. The feasibility and difference of the combined freezing artificial method in different height of water head are analyzed by model test. The experimental results show that: ①the connection for construction of frozen wall is positively correlated with formation head height, while the thickness of frozen wall is negatively correlated with formation head height. ② Affected by stratum freezing, the temporary shaft will have obvious frost heaving compression. With the development of frozen wall, the frost heaving force will appear two peak values, and finally decrease to a certain value, and then tend to be stable, and the peak value is correlated with head height. ③The maximum displacement point in the model test is 35 cm layer position, and the displacement data is 2 ~ 3 mm. ④ During excavation unloading, The temperature of frozen soil curtain maintain relative balance with the double action of excavation of foundation pit and active freezing. The relevant research results have certain reference value for the application of combined freezing method in foundation pit engineering.