天顶亮度是表征天空背景光的一个重要特性参数，为了获得天顶亮度变化特性，利用天空背景辐射测量系统对新疆某地区天顶亮度进行了观测，通过对实际测量数据进行分析，结果表明在天气晴朗时，天顶亮度与太阳高度角之间存在着一定的关系，给出了晴朗天气条件下天顶亮度随着太阳高度角变化的特征关系式，通过应用该关系式计算的结果与实测值的比较验证了该关系式的有效性。该特征关系式可用于晴朗天气时天顶亮度的实时监测，对天空背景光辐射亮度研究具有实际意义。

Zenith luminance is an important parameter of sky background radiation. In order to acquire the zenith luminance characteristic, the zenith luminance was measured with sky background measurement system at somewhere in Xinjiang. Experimental data was analyzed. The result indicated that there was a certain relationship between the zenith luminance and sun high angle in sunshiny days. A relationship formula between the zenith luminance and sun elevation in sunshiny days was proposed. The validity of the formula was verified through the comparison of the calculation data with the experimental value. This relationship formula can be used to analyze the zenith luminance in real-time in sunshiny days. It is valuable to research sky background radiation luminance.