Different from the measurement of plane illuminance in traditional lighting, panoramic illuminance is a parameter that evaluates the overall illumination of visible objects in space. Regarding its measurement method, in addition to introducing the existing approximate estimation method based on the measurement value of a cubic meter in six dimensions, a luminance distribution spherical function decomposition method based on the high dynamic range panoramic image is proposed, and a spherical light source is used to compare the accuracy of these two measurement methods. The results show that, compared with the former method, the latter method is more robust and will promote the use of digital equipment around to measure the panoramic illuminance.