A rectangular PCF structure in BK7 glass with inner and outer cladding is used to investigate effective mode field area, high nonlinear coefficient, and confinement loss and dispersion property using 2D FDTD technique. The PCF structure is purposed to design with pitches and air hole diameter in a periodic array fashion. The different properties of PCF structure like mode field area, nonlinear coefficient, confinement loss and dispersion are to be analyzed. The variation is investigated with change of different parameters like Ʌ1 , , and d1/d2 for a wide range of wavelength. The proposed rectangular PCF structure has slightly more nonlinear coefficient (γ= 36.98 W-1km-1) than the highly nonlinear silica photonic crystal fiber (γ = 35W-1 km-1) at a wavelength of 1.55µm with almost same mode field area (Aeff ~ 2.8µm2). This result seems to be important in super-continuum generation and nonlinear fiber optics.