Abstract: In this paper,aiming at the phenomenon of mixed-discrete variables which generally exists in engineering structural optimization,a simulated annealing approach is introduced to directly search the optimal solution without ‘specializing' treatment. According to the property of mixed-discrete variable problem,an adjacent producing function states is proposed, and a suitable annealing schedule to this optimzation is given.The results of two examples show that the simulated annealing approach can efficiently solve the engineering structural optimization with mixed-discrete variables.