The purpose of this article is to describe how to use demonstration and to initiate children's observation and imitation, in the same time to enhance the capability of problem solving by thinking further. Furthermore, this article focuses on the discussion of teaching practice. It helps preschool teachers to implicate on teaching by the reflection of the teaching process. By two teaching activities of making paper plane and straw glider, we can see the behavior of children's imitation through observation and improve their works.