Abstract: With particle swarm optimization technique, we designed a broadband low-profile microwave absorber based on resistive frequency selective surface. By designing the fitness functions, we discussed the influence of the optimization strategy on the result of design. Toward to the goal of broadband and low profile, we achieved an absorber with -10dB band-width from 6. 25 to 25. 30GHz, and thickness only about 3. 92mm. The design was validated by experiments, and the results was in a good agreement with the design for which the optimizing processing can be finished automatically.