Objective:To study the efficacy of astragalus polysaccharides combined with cisplatin in the treatment of malignant peritoneal effusion caused by ovarian cancer and its effect on drug resistance genes.Methods:Patients with malignant peritoneal effusion caused by ovarian cancer from January 2015 to December 2018 in Guangrao Country Hospital of Traditional Chinese Medicine were selected as the study subjects. They were divided into astragalus polysaccharide combined with cisplatin treatment group and cisplatin treatment group according to the odd and even number of hospital number, with 60 patients in each group. The patients in cisplatin treatment group were given peritoneal perfusion with cisplatin 75 mg/m 2 and 0.9% sodium chloride injection 50 ml, and the drainage tube were clamped once every 3 d. Treatment continued for 21 d. The patients in astragalus polysaccharide combined with cisplatin treatment group were treated with astragalus polysaccharide 250 ml intravenous drip once a day on the basis of cisplatin treatment group, and treatment continued for 21 d. The peritoneal effusion was pumped by drainage tube and was detected after treatment. The differences in adverse reactions, ascites recurrence time and median survival time were compared between two groups. Changes in inflammatory factors and T lymphocytes before and after treatment were detected and compared. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blot were used to detect resistance genes in peritoneal effusions including glutathione S-transferase π (GST-π), P-glycoprotein (P-gp) and multidrug resistance gene 1 (MDR1) mRNA and protein expression. Results:The incidence of gastrointestinal symptoms, Ⅲ-Ⅳ class myelosuppression and Ⅲ-Ⅳ class hepatorenal damage in the astragalus polysaccharide combined with cisplatin treatment group were significantly lower than those in the cisplatin treatment group [38.3%(23/60) vs. 66.7%(40/60), 6.7%(4/60) vs. 33.3%(20/60), 13.3%(8/60) vs. 45.0%(27/60)], while the ascites recurrence time and median survival time were significantly higher than those in the cisplatin treatment group [(6.3 ± 1.7) months vs. (5.5 ± 1.1) months, (15.2 ± 2.4) months vs. (11.7 ± 1.6) months], and there were significant differences ( P<0.05). There were no statistical differences in tumor necrosis factor (TNF)-α, interleukin(IL)-2, IL-6 between two groups before treatment ( P>0.05), after treatment in astragalus polysaccharide combined with cisplatin treatment group, the levels of TNF-α and IL-6 were lower [(21.8 ± 3.5) ng/L vs. (27.5 ± 4.1) ng/L, (17.2 ± 2.2) ng/L vs. (21.9 ± 2.7) ng/L] and the level of IL-2 was higher [(15.5 ± 1.6)ng/L vs. (12.7 ± 1.1) ng/L], and there were significant differences ( P<0.05). There was no statistical differences in CD 3+, CD 4+ and CD 8+ between two groups before treatment ( P>0.05), after treatment in astragalus polysaccharide combined with cisplatin treatment group, the levels of CD 3+, CD 4+ and CD 8+ were higher [(55.3 ± 3.9)% vs. (48.9 ± 3.2)%, (33.2 ± 3.4)% vs. (30.4 ± 2.2)%, (21.4 ± 3.1)% vs. (17.6 ± 1.9)%], and there were significant differences ( P<0.05). After treatment, the levels of GST-π, P-gp and MDR1 gene mRNA and protein expressions in astragalus polysaccharide combined with cisplatin treatment group were significantly lower than those in the cisplatin treatment group, and there were significant differences ( P<0.05). Conclusions:Astragalus polysaccharide can improve immune function and reduce drug resistance gene expression in patients with malignant peritoneal effusion caused by ovarian cancer, which can significantly improve the efficacy of cisplatin in the treatment of malignant peritoneal effusion caused by ovarian cancer and reduce adverse reactions.