The inclined long short composite pile has the advantages of good deformation control ability and low cost. Currently, there are limited studies on this aspect and understanding of its working mechanism is still lacking. In view of this, through the model test and numerical method, the deformation and mechanical characteristics of long and short inclined piles under different inclination and pile length combinations during excavation are studied, and then the working mechanism is discussed. The results show that: For inclined long short composite piles, the supporting effect is directly proportional to the inclination angle and inversely proportional to the pile length of row piles, and the influence of inclination angle is the greatest, followed by the pile length; When the total pile length is fixed and the short pile meets a certain embedded depth, the inclination angle has a critical value. When the inclination angle is less than the critical value, the optimal pile length distribution is affected by the inclination angle. When the inclination angle is greater than the critical value, the longer the inclined pile, the better the supporting effect.