In this paper,an experimental measurement system is designed to measure the stru cture constant of atmospheric refractive index C²_n using scintillation index method.The field experiment with link length of 2.5km is carried out in Xi′an area,and the variation trend of turbulence at night and the statistical characteristics of light intensity scintillation under three different weather conditions in Xi′an area are analyzed.The results show that under sunny,hazy a nd cloudy weather conditions,with the sequential change of weather,the constant value of atmosp heric refractive index structure measured by the experimental results decreases successively,the intensity of light flickering is reduced in turn,but the overall trend is the same,began to sever e changes in about at 19∶00,and at night in 7∶30 minimum.The exponential Weibull distribution is clo ser to the intensity scintillation probability distribution under experimental conditions, and the goodness of fit is greater than 0.96.The analysis of turbulence variation trend and the dis cussion of light intensity flicker probability distribution at night are of certain reference val ue to the channel research of wireless optical communication system in this area.