Since 1980's, there have been much progress on study of transition zone in upper mantle, in detection of both physical and chemical feature. Summarizing on study of transition zone in upper mantle using digital seismic data is given, and state of study using broadband seismic data is introduced. Up to now, there are still different views on feature of transition zone in upper mantle, especially for 670 km transition zone. On the basis of comment on researches after 1980's, this paper analyses the existing problem in the present and indicates possible direction of study.