Software cost estimation technology has become an important measure of software project management aspects of the control software schedule, reducing software risks and ensure software quality. In this paper, we use the model of C&S-PSO and weighted analogy estimates characteristic attributes to the weights. According to both MMRE and Pred (0.25) standards, we compare un-weighted analogy model, SRV, FNN and CART to estimate accuracy. Additionally, we use the non-parametric bootstrap method for raw data sampling, analysis PSO weighted analogy estimation model of stability. The results show that from the view of estimation accuracy the model of PSO has higher precision in weighted analogy estimates, and the model has also better stability.