The purpose of this study was to investigate that using of concrete materials in addition problem
was helpful or not to children\'s addition problem solving and was to analyze about children\'s
preference strategies in the process of addition problem solving. Forty one 5-year-olds solved 10
addition problems in each condition. In one condition, children had to solve using concrete materials
and the other condition had to solve non-using concrete materials in addition problem solving. The
study was used retrospective interview method, the results of this study were as follows. First, there
was a significant difference in children\'s addition accuracy scores between using and non-using
concrete materials. Children were more accurate in solving addition problem when concrete material
was used. Second, there was a significant difference retrieval, counting on from larger number,
counting all strategies in children\'s preference strategies for solving addition problems between using
and non-using concrete materials. Children frequently used retrieval, counting on from larger number
strategies in condition with using concrete materials and frequently used counting all strategies in
condition without using concrete materials in addition problem solving.