In order to improve the performance of the biogeography-based optimization(BBO)algorithm applied to optimization design of engineering structures, an improved BBO algorithm was proposed through introduction of a nonlinear model for migrating species and an idea of “elite guidance”. The improved algorithm was then applied to optimization design for structural engineering. Taking classical truss structures with two continuous variables as examples, optimization design of structures with a minimum mass under the constraints was performed. Numerical experiments show that the improved algorithm has faster convergence speed, better stability, and better performance as compared with the BBO algorithm, and can be effectively applied to optimization design of engineering structures.