6-Hydroxy-2-isopropyl-4-methyl pyrimidine (HIMP) could be decomposed by both photocatalysis and photo-Fenton reaction. The optimal condition for degradation of HIMP was photo-Fenton reaction with adding 2 ml of hydrogen peroxide at pH=3. Photocatalysis was little affected by the variation of pH, while photo-Fenton reaction was strongly affected by it. When salt(NaCl) was added, the photocatalysis was more active than photo-Fenton reaction.