Abstract: The effect of pile caps with various sizes on engineering properties of composite foundation with high strength pile was great.Specific data were collected from the settlement of a soft clay foundation in new double-line railway(v>200 km/h) project.4 sets of centrifugal model tests were conducted using CFG pile with different sizes of pile cap for soft clay foundation.The pile strain,distribution of pressure on pile caps and on earth,and stress of reinforcement were measured.It was shown that: ①The stability of embankments was raised by CFG piles with caps.②The larger the size of pile cap,the greater the variation of embankment and decrease of strain of reinforcement with increase of pile strain.③The reinforcement was distributed in a shape of M along the transverse section.The peak values occurred at the road abutment,indicating good agreement with the failure position of embankmats.