This study focuses on the soil of severely rocky desertification, simulating the photolysis process under various wavelengths of ultraviolet(UV) light in drought conditions. The aim is to investigate the decomposition and transformation process of easily extractable humus in severely rocky desertification under varying UV light exposures. The results indicated that: (1) Under various wavelengths of UV irradiation, the total carbon (TC) and total nitrogen (TN) levels in severely rocky desertification soil showed an upward trend as the irradiationtime increased. However, the decrease in the C/N indicated that the irradiation of UV light promoted mineralization and decomposition rate of humus. (2) The contents of primary amine, double bond, carbonate, and O—H of carboxy were stabilized after fluctuating change in the humus easily extracted from the severely rocky desertification soil. They affected the hydrocarbon-generating process to varying degrees depending on various wavelengths of UV irradiation. (3)With increased irradiation time, the substituent group on the benzene ring of the easily extractable humus gradually became dominated by aliphatic chains, the degree of aromatization was enhanced, and the hydrophobic component was increased under UVA and UVB irradiation. In conclusion, ultraviolet radiation in different wavelengths could affect the capacity for hydrocarbon generation, promote the condensation and aromatization of easily extractable humus, and accelerate the process of soil humus mineralization.