The polarization pattern of full moonlight in clear sky is investrgated in order to understand the distribution law of polarization properties of full-sky scattered light better. Night skylight sources have been investigated. The polarization pattern of full moonlight has been simulated based on Rayleigh scattering theory. The distribution patterns of full moonlight, twilight and sunlight as well as the distribution patterns of continuous observation from twilight to moonlight have been acquired using a full-sky imaging measurement system. After contrasting and analyzing the neutral point and the orientation of meridian line, it is proved that the polarization pattern of full moonlight in clear sky is basically consistent with the simulation results, and it conforms to the Rayleigh scattering theory; the twilight polarization pattern is affected by sunlight and moonlight simultaneously; when the altitude angle of the sun is similar to that of the moon, the distribution trends of polarization patterns are identical; the power of the light does not change the value of skylight polarization distribution patterns.