[Objective] To observe the inhibitory effect of Baihu Decoction (BD) on adverse reaction induced by photodynamic therapy (PT) in malignant tumor patients. [Methods] Fifty-six malignant tumor patients receiving PT were equally randomized into group A and group B. The two groups received routine symptomatic western medicine treatment, and anti-inflammation treatment. Group A was treated with BD additionally. [Results] Incidence of fever was 28.6% and that of pain was 85.7% in group A, and 57.1% and 100% in group B respectively (P 0.05). Duration of fever, pain and edema was respectively 2.73?0.58, 6.71?0.81 and 5.25?0.94 days in group A, and respectively 4.56?0.76, 9.12?1.14 and 8.84?1.01 days in group B (P 0.05). In group A, there were 11 patients with white blood cell (WBC) count over 10?109/L, and the average WBC count was (10.6?2.36)?109/L; there were 18 patients with WBC count over 10?109/L, and the average WBC count was (14.3?3.17)?109/L. The difference of WBC count was significant between groups A and B (P