The factors influencing photochemical degradation of petroleum on soil surfaces under simulated visible light, such as the initial oil concentrations, soil types and pH, were investigated. The concentrations of petroleum in photolytic processes were analyzed by UV-Vis. GC-FID and FTIR were used for the characterization of petroleum hydrocarbons. Experimental results indicated that photochemical degradation of petroleum on soil surfaces followed pseudo first-order kinetics with the rate constant of 0.0026-0.0172 h(-1) and half-life of 40-267 h. GC-FID analysis showed that, after 50 h of irradiation, the content of saturated hydrocarbons with longer chain decreased, while the proportion of shorter chain ones increased slightly; in addition, most chromatogram peaks of aromatics weakened or disappeared. After 60 h of photolysis, the appearance of carbonyl compounds in FTIR spectra of the extract from soil demonstrated that petroleum was gradually oxidized in the photolytic process.