The aim of experimental study is testing of the possibility and efficiency of conservation understanding formation in preschool children through the formation of their logical operations of classification and seriation. New training methods of classification and seriation were developed. They are based on the mastery of the actions belonging to the composition and structure of the data logic operations. Parallel formation of logical operations of classification and seriation using these new techniques allowed the subject not only to master these logic operations in a full, but also let the children overcome nonconservation phenomena. The possibility of formation of some concrete-operational structures of intelligence (understanding of the conservation principle) through other specific-operational structures of intelligence (the composition and structure of logical operations of classification and seriation) was proved for the first time.