Abstract: In order to improve the solution quality of PSO with constrained problems, by converting equality constraint to inequality constraint through reduction stategy, the numbers of designed variables and dimensions of particles are reduced; meanwhile, by placing inequality constraint into subroutine beforehand, solutions that not within the solution space are excluded before using PSO optimization to calculate the fitness function so that the optimization calculation is reduced. By using informations of other particles during the optimization, inertia weights of PSO algorithm are adjusted, also, the optimization steps of the weighted PSO with constraint problems are given. By respectively dealing with the equality constraint, the inequality constraint and both of them through the weighted PSO and the tradional PSO to optimize two typical examples, from the comparisons of the optimal values, mean values, standard deviations and average optimization times which are obtained from the calculations of the examples, it is showed that the method of simultaneous processing to the constraint conditions by using weighted PSO can improve both the accuracy and effiency of the solutions.