The object of this article is to claim importance of reflective thinking when using problem-solving method in "Preschool Practicum". To propose Karl Popper's and John Dewey's idea for problem-solving process and they both encouraged positive action about trial-and-error. Problem-solving teaching can be separated as following: find a problem, analyze the cause of the problem, form solutions, and teaching practice. In addition to focus on reflective thinking and review after practical teaching, and it is helpful to form personal experiences through reflective thinking and review. Those students who are willing to think their practical teaching reflectively have positive working attitude. The teacher has to guide the students how to be reflective thinking in problem-solving teaching process.