Abstract: We use the microgenetic design to examine 30 6-age-old children's acquisition of matrix completion proficiency.The results are as follows:from the source of change,experimental manipulation is a important source of strategy discovery in figure reasoning task;from the variability of change,children are followed learner model of strategy discovery;from the path of change,the main error are orientation err and size err in all three groups.In norm group and latter group,there are also other errs displayed.When the children in quick group arrive the crite-rion of strategy discovery,their accuracy would likely come down;but in other two groups,the can maintain high accuracy;from the rate of change,children in the first three sessions display rapid changes in accuracy,however, their accuracy will maintain in high level in other sessions.

Key words: figure reasoning, strategy discovery, microgenetic developmental processing