Based on analyzing the deformation mechanism of composite foundation, the maximum settlement calculation of rigid-pile composite foundation by method of compression of cushion between pile top and foundation is proposed. In the calculation the pile settlement is estimated from pile loading test data in the past. The main problem is then to focus the compression calculation of the cushion between pile top and foundation. The variation of the compression modulus of the cushion with loading level is considered in the calculation. The calculated results are compared with that collected from 28 actual projects, and three projects of them are introduced in detail. The calculated results accord well with all measured data.