To examine the effect of volume of grouting reinforcement body， namely the size of the expanded foot， on the bearing capacity of pile tip， indoor single-pile static-load model tests were conducted through injecting grout into PVC pipe and changing grout amount and PVC pipe size to control the size of the expanded foot. Finally， the pile tip resistance-displacement curves were calculated by the traditional pile tip settlement formula and compared with the measured curves. The results show that when comparing with the pile without grout injection， the piles that form expanded foot after being injected cement soil show the significantly improved bearing capacity， and dramatically reduced settlement under the same load; As the diameter of expanded foot increases， the bearing capacity continues to rise; However， the bearing capacity improved with the increase of per unit diameter at first and then decreased， and its effect on reducing displacement under working load shows a decline trend; The sharing ratio of tip resistance tends to be stable after a displacement of 5 cm. The cement soil expanded foot on pile tip has high ratio of tip resistance and the ratio rises as expanded foot diameter increases. In practical engineering， more importance should be attached to the strength of cement soil on pile tip for the high stress of cement soil， and the pile tip resistance-displacement curves calculated by using traditional pile tip settlement formula fit the measured curves well.