Abstract：Objective：To observe the clinical effect of modified Zhishi Baizhu Decoction for functional constipation with deficiency of both qi and yin syndrome. Methods： A total of 96 cases of patients with functional constipation with deficiency of both qi and yin syndrome were divided into the control group and the trial group according to the random number table method， with 48 cases in each group. The control group was given oral administration of Ziyin Runchang Oral Liquid， and the trial group was treated with modified Zhishi Baizhu Decoction. Before and after treatment，symptom scores of constipation，scores of Patient Assessment of Constipation Quality of Life (PAC- QOL)， number of spontaneous defecation per week， and levels of motilin (MTL)， vasoactive intestinal peptide (VIP) and gastrin (GAS) were compared between the two groups. The clinical effects and incidence of adverse reactions were evaluated between the two groups. Results：The total effective rate was 93.75% in the trial group，higher than that of 79.17% in the control group. After treatment，the symptom scores of constipation，the PAC-QOL scores including physiological， social psychology， concern， and satisfaction degree， and VIP levels in serum in the two groups were decreased when compared with those before treatment (P＜0.05)， the number of spontaneous defecation per week was increased (P＜0.05)，and the levels of MTL and GAS in serum were increased (P＜0.05). After treatment， the symptom scores of constipation， PAC- QOL scores， and VIP levels in serum were lower than those in the control group (P＜0.05)， and number of spontaneous defecation per week was more than that in the control group (P＜0.05)， and levels of MTL and GAS in serum were higher than those in the control group (P＜0.05). There was no significant difference being found in the comparison of the incidence of adverse reactions between the two groups (P＞0.05). Conclusion： Modified Zhishi Baizhu Decoction has a definite curative effect in functional constipation of deficiency of both qi and yin syndrome type，which can effectively improve the gastrointestinal function and quality of life，with high safety.