Inclined pile combined support is a new type of foundation pit support, which is suitable for large area foundation pit without internal support. In this paper, based on a sloping piles supporting of foundation pit project of Tianjin, the design of 6 kinds of precast pile supporting structure, including four kinds of combination of inclined pile supporting, to carry on the excavation of large field test, measurement analysis under different environment surrounding the combination structure supporting the deflection of the foundation pit, and the finite element software Plaxis 3D analysis of the stability of foundation pit. The results show that among the different types of inclined pile combination support, the inner inclined straight combination pile displacement is the least and the supporting effect is the best. When there are adverse factors around the foundation pit, such as over-digging, it is obviously different from the conventional pile row. The rigid frame effect, the diagonal brace effect and the gravity effect of the inclined pile combination support determine that it can still play a good role of its own stability. And the influence of soft soil creep on inclined pile foundation pit support should not be ignored, when the excavation reaches the bottom of the pit, cushion and floor should be constructed in time. Numerical simulation analysis shows that the influence of over-excavation on the safety factor and critical failure mode of foundation pit for inclined pile combination bracing is less than that for conventional pile row bracing, and small over-excavation has little influence on the stability of foundation pit.