The experiment of photolyzing prilled ADN with sunlight on solid phase were carried out to investigate the effect of photolysis on the purity，sensitivity and the apparent storage life of ammonium dinitramide. The process of photolyzing ADN was measured by IR analysis，the purity and apparent storage life of photolyzed ADN were tested by the liquid chromatogram. The result indicates that the product of photolysis is ammonium nitrate，and the apparent storage life of ADN photolyzed with sunlight are 756.2 days. The appearance of photolyzed ADN is analyzed by SEM. The friction and impact sensitivities of ADN all reduce，which were tested according to military standard of China. So the purity of ADN reduces after photolyzing，but the decomposition of ADN is restrained because ADN grain is coated by the crystal of sphericized AN formed from the photolyzing.