Abstract: As the core component of the steam ejector refrigeration system (ERS), the performance of the steam ejector has a significant impact on the overall system's operation, directly determining the refrigeration efficiency. The adjoint method is applied to the ejector field, and a visualization scheme is established for sensitivity analysis to identify key structural parameters. The range of levels for the key parameters is determined through single-factor analysis, and an L₉(3⁴) orthogonal table is constructed to derive the optimal structural parameter combination. The adjoint optimization method is further applied to optimize the main nozzle structure of the optimal parameter combination. The study shows that the adjoint method can quickly identify key regions affecting performance in complex geometries. The optimal parameter combination obtained through orthogonal experiments improves the ejector's entrainment ratio (ER) by 7.6%, while the adjoint optimization method further increases the ER by 26.7%. The use of a segmented convex curve for the nozzle contraction section enables a smoother fluid acceleration process in the nozzle region, reducing energy loss and significantly enhancing the ejector's performance.