This paper introduces a method of determining the bearing capacity of rotary jet grouting piled composite foundation, and in combination with the on-site experiment of rotary jet grouting piled composite foundation in Shenzhen area, makes the analysis on the bearing capacity of the composite foundation. It is confirmed that while utilizing the formula to estimate the characteristic value of capacity, the values of R_a, f_sk and β should be properly chosen. The determination of the characteristic value of capacity is studied when the range is 30% greater than that of the average in the static load test. Accordingly, a method is put forward to convert the bearing capacity of composite foundation by different pressure plate area load tests to the actual bearing capacity of composite foundation.