In recent years, web based online map applications have been getting more and more popular, such as Google Maps, Yahoo Maps. Many new Web 2.0 techniques such as mash-up and AJAX were adopted in these map applications to improve user experiences. But few researches have been done on traffic analysis of the Web 2.0 based online map applications. In this paper, we introduced our research on features of online map applications that previous studies hadn’t cover. In our research, we captured map application related HTTP traffic in a campus network while not violating user privacy. We introduced the traffic overview, mash-up and web caching characteristics of four map web sites (Google Maps, Yahoo Maps, Sogou Maps and Baidu Maps). For the first time, the mash-up characteristics of Google map traffic were analyzed using a new method proposed in this paper. The same method could be applied to other mash-up analysis works. These results can help us optimize the future web application designs...