Abstract: In this paper, the shaft radius, the length of the shaft section and the radius of the shoulder radius are taken as the reference factors. The maximum stress of the dangerous point is used as the evaluation index to optimize the structural parameters of the horizontal axis of a contact radial force loading mechanism. Using the finite element analysis parameter sensitivity, considering the design economy, the control variable method is used to quantitatively analyze the shaft radius and the shoulder radius. When the volume of the shaft is kept as small as possible, the stress at the dangerous point is significantly reduced, and finally the safety factor and reliability of the horizontal axis are checked.