The invention discloses an optimization method of shield excavation parameters under the condition of a compound stratum. The method is characterized by comprising the following steps of (1) carrying out shield excavation orthogonal experimental design; (2) collecting excavation data; utilizing a data collection and storage system of a shield tunneling machine to collect and record experimental data; collecting the thrust, the rotating speed of a cutter, the excavation speed, the foam solution adding amount, the foam concentration and the cutter torque by the data collection system during the experiment process; collecting data at a time after excavating 20mm every time, wherein the experimental excavation length of each group is 1.6m; (3) building a shield excavation parameter mathematical model; designing an orthogonal experimental model according to the shield construction process, carrying out nonlinear regression analysis on data collected by the orthogonal experiment, respectively building an excavation speed model and a cutter torque model of earth pressure balance shield, confirming the reasonable excavation parameters under the condition of the compound stratum through resolving, and optimizing the excavation parameters, so that the safety of shield construction is improved, and the service life of the shield tunneling machine is prolonged.