In this paper, we introduce ‘Racetrack Principle’ and study on understanding of physical meaning and
inequality of differential calculus. Based on this research, an actual lesson was done in the field of high
school by introducing ‘Racetrack Principle’, students didn't have much difficulty in comprehending physical
meaning of ‘Racetrack Principle’ and ‘Differential Calculus’ and showed higher level of achievement in
solving problems, applying this principle. Thus, if ‘Racetrack Principle’ can be adopted seasonably in the
field of school, students will be able to realize the relation between mathematics and real life and develop
mathematical power to enable students to observe changes of phenomenon, which will ultimately serve as a
momentum for them to acquire functional thinking.