In this study, a combined performance-based seismic failure mode identification and multi-objective optimization method is proposed, in which the failure probability function is introduced to identify the primary structural failure mode with a certain probability level, and the structural damage and hysteretic energy are taken as indices in the objective function to improve the structure's seismic performance. Taking a 20-story steel frame structure as an example, seismic failure modes are identified and optimized using this method. Results indicate that global damage to the optimized structure is reduced under 62% earthquake excitations, while the hysteretic energy dissipation capacity of the optimized structure is improved under 48.3% earthquake excitations. Furthermore, the distribution of the optimized structure's inter-story drift ratio is more uniform than in the original structure, leading to a significant improvement of the structural seismic performance.