Abstract: In order to lighten the structure, the frame of subsoiler in dryland orchard was analyzed and optimized by finite element method.The maximum subsoiling resistance is obtained by motion simulation analysis of the process of subsoiling knife cutting soil.The stress of the frame is determined through mechanical analysis and calculation.The ultimate load strength analysis of the frame is carried out in the workbench.It is obtained that the maximum stress of the frame is 67.8 MPa, which does not reach the allowable material stress of 117.5 MPa.It is verified that the reliability of the frame work and there is a large stress margin.In this paper, the response surface optimization method is used to optimize the design of the frame.Taking the frame mass and the front-end stress of the steel pipe of the rear suspension hook as the objective function, the frame optimization mathematical model is constructed.Based on the box Behnken test design principle, 17 groups of test models are selected for simulation test, and the least square method is used to fit the test results.Taking the minimum mass and stress no more than 110 MPa as constraints, the optimal parameter combination is obtained.After optimization, the stress value of the frame is 89.8 MPa and the mass is 53.2 kg.Through field experiments, the average values of stress measured in three experiments are 78.3 MPa, 77.7 MPa and 79.4 MPa, and the simulation error is no more than 13%,which verifies the accuracy of the optimized mathematical model.The optimization results show that on the premise of ensuring the working reliability of the rack, the weight of the rack is reduced from 62.2 kg to 50.1 kg, with a decrease of 19.4%. The weight reduction effect is obvious, and the optimization goal is achieved.