PBL (Problem-Based Leaning) is recognized as they key of successful instructional method. Teachers use PBL to teach problem solving and to replace traditional memorization and passive learning. PBL's benefits, its process, its differences for traditional teaching are also discussed. And, the purpose of this article is to share the experience of how implementing PBL teaching materials on the environmental issue for fifth grader. Finally, several difficulties concerning PBL teaching method used in an elementary course are also pointed out.