In this paper, constrained interpolation profile (CIP) and rational function-interpolation profile (R-CIP) methods are applied to electromagnetic field analysis for the fundamental examination. And the dependency of Courant Friedrichs Lewy (CFL) condition is examined using FDTD, CIP and R-CIP method when a rectangle wave propagates. As a result, it is confirmed that the computational values by three methods agree well with that of theoretical one when CFL condition is equal to 1, however, the computational value is oscillated in FDTD method and that is diffused in CIP and R-CIP methods when CFL condition is less than 1. And the calculated results using FDTD, CIP and R-CIP methods in rectangle wave propagation is confirmed