Determination of azimuth angle of photonic crystal fiber is essential in the fabrication of devices based on photonic crystal fiber. The side images of hexagonal、hybrid and large mode area20 structures of photonic crystal fibers were studied by illuminating the side of photonic crystal fibers vertically. The side images vary with the rotation of the fibers, and they display special light intensity characteristics. The characteristic values of images show periodic variation, which is corresponding with the inner structure of photonic crystal fibers. Simulation analysis for photonic crystal fibers were made by Tracepro software, the results of simulation show that the characteristic values of side images change with the rotation of fiber, and they perform the similar features with the experimental research. Compared with the characteristic curve of the experimental and the simulation results, the characteristic values has maxima values around the vertex direction of hexagonal structure formed by air holes, and it can be used to distinguish azimuth angle of photonic crystal fibers.