In program analysis, there is an emerging trend to apply probabilistic reasoning. In general, these approaches build their models based on probabilistic graphical models because they can express local correlations through factors in a compositional manner, which is suitable for program analysis. These models commonly use the loopy belief propagation algorithm to infer the marginal probability distribution for efficiency. However, the efficiency of loopy belief propagation is still affected by large factors. To address this challenge, our insight is that we can exploit the local structure of probabilistic constraints to speed up the inference. To realize this idea, we use if-then rules to encode the factors with local structures and propose an efficient loopy belief propagation algorithm based on it. We also discuss the inference algorithm complexity and prove some applicable conditions of our approach. Our approach is evaluated on two existing program analysis works based on probabilistic graphical models. The results show that our approach can be 5.11 and 2.31 times faster than the original loopy belief propagation algorithm on average, respectively.