Abstract: Objective To investigate the relationship between serum microRNA-143 （miR-143） level and chemosensitivity to paclitaxel in patients with advanced gastric cancer. Methods A total of 82 patients with advanced gastric cancer treated with paclitaxel-based regimen in our hospital from January 2012 to July 2016 were enrolled. Serum samples were collected before chemotherapy and their miR-143 levels were detected by qPCR method， and then compared with 76 healthy persons in the same period of miR-143. The relationship between different miR-143 levels and clinical pathological characters were analyzed. RECIST1.1 standard was used to evaluate the short-term efficacy and the relationship between different levels of miR-143 and chemosensitivity were evaluated. Median progression free disease （PFS） and survival （OS） were compared between different miR-143 levels according to follow-up data. Results The qPCR detection showed that the miR-143 level of 82 patients with gastric cancer was （0.215±0.021）， lower than those of the healthy subjects （1.099±0.057）， and the difference was statistically significant （P<0.05）. Serum miR-143 level was not related to sex，age， ECOG score， tumor location and pathological type， but with TNM stage and differentiation degree，and the difference was statistically significant （P<0.05）. The serum miR-143 level of 31 patients with chemotherapy sensitive （CR+PR） was （0.341±0.040）， which was higher than that of chemotherapy resistance （SD+PD）in patients （0.138± 0.015），and the difference was statistically significant （P<0.05）. The patients were divided into high expression group （>0.177） and low expression group （≤0.177） according to the medium value. The response rate， median PFS and OS in the high expression group were 48.8%， 8.5 and 12.2 months， significantly better than those in the low expression group （31.7%， 7.3 and 9.4 months）， and the difference was statistically significant （P<0.05）. Conclusion The serum miR-143 level of advanced gastric cancer is lower than normal， and related to the paclitaxel chemotherapy sensitivity and prognosis. High expression of miR-143 had a higher sensitivity and better prognosis，showing a certain value in the diagnosis and prognosis of gastric cancer.