The impacts of phase errors induced by the fabrication errors on the transmission characteristics of an AWG are studied in this paper. The non random phase error makes the central wavelength of the channels shift, the studies show that when the 0 02 μm change of the width of the waveguide will cause 0 1 nm shift of the central wavelength. The random phase error deteriorates the crosstalk of an AWG, the studies show that the maxium random error of 0 00004 rad/μm will make the crosstalk increase 42 dB.