The miniature CFG pile has been widely used in guilin area of Guangxi.In order to provide theoretical basis for the development and study of CFG pile used in red clay layer,through in-situ test study on outdoor full scale miniature CFG pile,the article studied the increase coefficient of bearing capacity,exertion coefficient of bearing capacity of single pile ,and stress ratio of pile to soil in empirical formula of bearing capacity of composite foundation among piles.The experimental results demonstrate that when the length of miniature CFG pile is in the range of one to four meters, the coefficient of bearing capacity between piles increases with the increase of pile's length,but the trend of increase gradually decreases. The coefficient of bearing capacity of single pile decreases with the increase of pile's length.when pile length is one to three meters, the exertion coefficient of bearing capacity of single pile is greater than one.When the pile length is greater than or equal to three meter,the coefficient of bearing capacity of single pile is less than one.When the stress ratio of pile to soil is between one and eight,The coefficient increases with the increase of pile length.