The label propagation algorithm, a commonly used community discovery method, has approximately linear time complexity but randomness and instability. To solve the problems of low accuracy and poor stability of the label propagation algorithm, this study proposes an improved Label Propagation Algorithm based on node Importance and Similarity (LPA_IS). First, based on node importance, a method is proposed to obtain the seed node set and the algorithm update sequence. Second, a method is proposed with node importance and similarity to calculate the comprehensive influence of labels. Any node updates its own label according to the comprehensive influence of its neighbor labels. Experiments on real networks and synthetic networks have shown that compared with five typical label propagation algorithms, LPA_IS can improve the accuracy and stability to a certain extent and reduce the iterations.