In the field of atmospheric optics, distribution of sky brightness is widely used. The theory of sky brightness measurement is briefly introduced. A new design scheme of intrument for sky brightness measurement used in the day in visible and infrared band is proposed based on kindred instrument analysis, and the structure and selection of detector are introduced. After calibration, the instrument can get absolute value of sky brightness, which can show variety of sky brightness distribution. The instrument perfects traditional instrument for sky brightness in wave bands, characters of real time and portability, and meets practical demand in scientific research.