A wireless optical link in length of 610 m is established in Lanzhou area to investigate the light intensity distribution and fluctuation characteristics of Gaussian laser under different weather conditions. The three-dimensional pseudo-color transform method is utilized to analyze the spatial distribution of light intensity. The results show that the intensity distribution of the main lobe within the light spot follows the Gaussian distribution. The steepness of light intensity distribution decreases and the attenuation of light intensity increases according to the order of sunny day, cloudy day and overcast day in turn. Moreover, the atmospheric scintillation index is analyzed by using the measured light intensity data. The results show scintillation index of sunny day, sunny day after rain and overcast day are 0.225 4, 0.189 2 and 0.188 8, respectively. This indicates that the light intensity fluctuation in sunny day is higher than sunny day after rain and overcast day. The probability density distribution of light intensity is obtained by using nonlinear fitting of histograms of the normalized optical intensity data. They all conform to log-normal distribution. Especially, the probability density in sunny day is more consistent with log-normal distribution, the goodness of its fitted curve is up to 0.997 50.