Abstract: Oil film dampers are common supporting components for high-speed rotating machinery, which have the advantages of a simple structure, an easy installation mode, and dependable performance of performing the functions of ensuring rotor system stability and controlling rotor amplitude. An ordinary oil film damper is made up of three parts: a damper shell, damping medium and a damping mandrel submerged in the medium. It has been demonstrated that optimizing the structural parameters of an oil film damper is an effective way to improve its supporting and damping performance. Therefore, the research goal of increasing the stability of the rotor system at rated speed can be accomplished by optimizing the damper’s structural parameters. In the preceding research, a numerical calculation method for analyzing the supporting properties of an oil film damper was proposed considering the wedge clearance effect. Using the mentioned numerical method, this paper conducted additional research and put forward an fitting formula method for optimizing the damper’s structural parameters, in order to extend the range of values for the structural parameters during the optimization process, reduce the cost of performance verification in the manufacturing and testing processes, furthermore, enhance the iterative efficiency of the optimization on structural parameters compared with the traditional design process of component verification test. The numerical experiments under the structural parameters with crossing settings were firstly carried out. The force parameters, such as the radial restoring force and tangential damping force, as well as the supporting parameters, such as the radial stiffness coefficients and tangential damping coefficients of the damper that correlate to different structural parameter combinations were identified. Then, the fitting function expressions of the damper’s force parameters and supporting parameters with the variation of structural parameters were calculated using the multiple linear regression method within a specified range of structural parameters. Lastly, the structural parameter schemes of real dampers were used to validate and verify the obtained fitting function expressions. By contrasting the function expressions’ calculation results with the experimental results, the rationality and accuracy of the function expressions were checked. Hence, the features of the function expressions to design, optimize and forecast the damper’s structural parameters within a specified range were determined. The function expressions can be used to inversely calculate the damper’s structural parameter schemes that match the rotor system parameters’ requirements. This study demonstrates that the fitting formula method, which is based on multiple linear regression fitting method, is effective for optimizing the structural parameters of an oil film damper. This fitting formula method has the potential to enhance the design and verification efficiency of multi-scheme structural parameters in a parallel mode.