The purpose of this study was to examine the relationship between the number conservation task and the successive information tasks (digit-span and Knox-Cubes) in preschool children. The latters were classified in two types of processing; forward (maintaining) type and backward (transformational) type. The suggestions of the results were as follows: (1) backward type successive information tasks had a stronger relation to the conservation task than forward type, and (2) the common function between the backward type tasks and the conservation task was not a spatial ability, but an ability to transform information. Information integration in preschoolers was discussed in relation to Das's information processing model and it was supposed that to transform information was one of the planning functions at frontal lobe of human brain.