To study the application of continuum structural topology optimization methods to real engineering structures, an optimization method for an optimal topology design of multistory steel frame bracing systems is presented. On a sensitivity analysis, an element removal criterion for continuum structures with stress and multi-displacement constraints under multiple lateral loading conditions is proposed. A concept of mean thickness of a design domain is provided to ensure the reasonableness of optimal results. In the proposed optimization method, the optimal design of an unbraced steel frame without displacement constraints is performed firstly, and then the optimal topology of a bracing system for the multistory steel frame considering displacement constraints is obtained by using evolutionary structural optimization and the given removal criterion, and finally the optimal layout of the bracing system is interpreted as bracing members. An example of 3-bay 12-story plane steel frame shows that it is effective for the given optimization method in the optimal design of bracing systems for multistory steel frames.