In view of the characteristics that the settlement of pile raft foundation is in the linear elastic stage under design load, based on the vertical stiffness of single pile obtained from the static load test curve, relevant theories and empirical formulas, the calculation method of the overall vertical stiffness of pile raft foundation is established. On this basis, the practical calculation method of the average settlement of pile raft foundation under working load is proposed. Through the comprehensive analysis of the field measurement and calculation results of 8 engineering cases in 4 categories of high-rise building foundation in soft soil area and loess area, rock-socketed pile foundation and large traffic engineering, the validity of the proposed method is examined. The calculated settlement value is basically 0.8~1.5 times of the measured settlement, which verifies the reliability of the proposed settlement calculation method in practical engineering. In addition, the calculation method can provide reference for the preliminary design of settlement calculation of actual pile raft foundations.