Abstract: The research selected 33 grade 2 students of a primary school,among whom boys and girls are half-and-half.Their age is between 83 and 106 months.The average is 94 months.Microgenitic design was used.Children's memory performances were tested in 5 independent interval using a words list including 15 words within 3 categories.The Results were as follows:(1) during the development of the category memory strategy,there are the processes of sudden change as well as gradual change,category encoding strategies had production def iciency,category retrieval strategies are spontaneous gradual changing process.,and both of them will increase suddenly after training;(2) when tasks are unfamiliar,a few children have the phenomenon of the category encoding strategies and retrieval strategies applying defects.

Key words: the microgenetic method, encoding strategies, retrieval strategies, applying defects