Research on the polarization patterns is of great importance to reduce polarization disturbance errors, improve measurement accuracy and optimize system design. Scattering angle (SA) and degree of polarization (DOP) of skylight are measured by vector polarization measurement system under different sky conditions. The experiments demonstrate that all relationship curves between SA and DOP can be described as parabolas regardless of sky conditions. DOP changes with sizes of atmospheric scattering particles. When the sizes of the particles increase, DOP decreases and SA drifts. A single light scattering polarization model based on Mie theory is proposed to analyze the experiments. Simulation results are in good agreement with the experimental results.