A constrained interpolation profile (CIP) method[6][7] is payed much attention because of its accurate simulation result compared with conventional FDTD method. In this paper, on scattering problem by a dielectric cylinder with high contrast with its background air, performance of CIP method is compared with analytical approximated method using Hertzpotential [8] and conventional FDTD simulation [9]. As a measure of accuracy of CIP and FDTD simulation, an normalized cross correlation function is defined and compared with it, by setting analytical approximated result as a reference. Consequently, results of CIP method showed better correlation than that of FDTD method. As applications of CIP method, analysis of electromagnetic field propagation in Y-shaped branching waveguide and Mach-Zehnder interferometer in two dimensional photonic crystal structure were demonstrated. Both of analysis results showed reasonable behaviour. Especially for asymmetrical Mach-Zehnder interferometer, the measurement result by microwave model and the numerical result of CIP corresponded to each other. Complicated output characteristics of asymmetric Mach-Zhender interferometer was interpreted very well by refering to the electric field profile obtained by CIP method.