The study on topic evolution can help people to understand the ins and outs of topics. Traditional study on topic evolution is based on LDA model, but for microblog data, the effect of this model is not significant. An MLDA model is proposed in this paper, which takes microblog document relation, topic tag and authors relations into consideration. Then, the topic evolution in content and intensity is analyzed. The experiments on microblog data have shown the effectiveness and efficiency of the proposed approach to topic detection and evolution analysis on Microblog.