By finite difference method,the spectrum of photonic crystal fibers with high-index inclusions is obtained and its application for sensor designing is discussed. The simulation of transmission spectrum of this fiber with different rings of cladding holes is carried out. In the case of two rings of holes,a suitable passband is found and its stop wavelength changes with high sensibility,almost linearly,as the index of inclusions changes. In average,the wavelength changes 24 nm when the index changes 0.01 in range of 1.48～1.8.This conclusion implies that the novel photonic crystal fiber sensor has high sensitivity and wide measuring range.