With an aim to study the bearing capacity of concrete pipe piles in foundation pit supports, an indoor model test of its horizontal bearing capacity has thus been made of 6 sets of concrete pipe piles of different inner diameters in 2 groups, after a filling treatment as well as a non-filling treatment, followed by an analysis of the horizontal bearing capacity of concrete pipe piles of different diameter and with different core strengths after the excavation of foundation pits. Experimental results show that the core filling can effectively improve the foundation pit supporting performance of the concrete pipe piles. With the external diameter a constant, the longer the pile diameter is, the greater the effect exerted by the excavation on the pile foundation pits will be. Thus the core filling and reinforcement help to effectively enhance the safety of pipe pile supports.