Objective: To observe the clinical efficacy of Zengse Pill (增色丸, ZSP) on patients with vitiligo of qi-stagnancy and blood-stasis syndrome type (V-QB), and to preliminarily explore its mechanism of action. Methods: Sixty-five V-QB patients, with their diagnosis confirmed by clinical examination, were randomized by digital table method into two groups, with 31 patients in the control group and 34 in the treatment group. Cobamamide (2 tablets) was administered orally to all patients, and Psoralea tincture (a self-formulated preparation) was applied externally thrice a day. In addition, for patients in the treatment group, ZSP was given orally, at 5 pills per dose, 3 times every day. The therapeutic course for both groups was 3 months. Patients were re-examined every half-month, and changes in the skin lesions were observed and recorded. The levels of lymphocyte subsets, serum immune globulin, and complement C3 and C4 in patients were determined before and after the therapeutic course and compared with the corresponding indexes determined in 21 healthy subjects. Results: The total effective rate in the treatment group was 82.4%, which was markedly higher than that in the control group (54.8%), showing a significant difference (P