The inversion calculation method about aerosol optical depth(AOD) and Angstrom wavelength exponent was given by using the sun photometer CE318. The aerosol optical depth and wavelength exponent in Gobi area of Xinjiang were statistically analyzed and five kinds of typical daily variation model about aerosol optical depth were given. The characteristics of season variation about daily average were given, the minimum AOD in June to August is 0.1, and the maximum mean in April is 0.73. There is an inverse correlation about wavelength exponent and AOD. The AOD in Gobi area is influenced by the particle diameter of sand dust.