Objective To investigate the expression levels and prognostic value of preoperative serum exosomes micro RNA(miR)-193a and micro RNA(miR)-208b in patients with gastric cancer(GC).Methods A total of 132 patients who underwent GC radical gastrectomy in the First Affiliated Hospital of Xinjiang Medical University from March 2018 to March 2020 were regarded as the GC group,while 132 healthy individuals who underwent physical examination were selected as the control group.Their clinical and pathological data were collected and compared.The relative expression levels of miR-193a and miR-208b in serum exosomes were detected using quantitative real-time polymerase chain reaction(qRT-PCR)method.Pearson method was used to analyze the correlation between miR-193a and miR-208b.The correlation between the expression of miR-193a and miR-208b in preoperative serum exosomes of GC patients and postoperative prognosis was analyzed using Kaplan-Meier method.Univariate and multivariate COX regression were applied to analyze the influencing factors of prognosis.Results The expression level of miR-208b in the serum exosomes of the GC group was higher than that of the control group(1.77±0.14 vs 1.02±0.01),while the expression level of miR-193a was lower than that of the control group(0.52±0.06 vs 1.01±0.01),and the differences were statistically significant(t=92.551,61.392,all P<0.05).The expression levels of miR-193a and miR-208b in GC patients before surgery were negatively correlated(r=-0.409,P<0.05).The low expression rate of miR-193a and high expression rate of miR-208b in patients with TNM stage Ⅰ+Ⅱ,no lymph node metastasis,and no distant metastasis were lower than those in patients with TNM stage Ⅲ+Ⅳ,lymph node metastasis,and distant metastasis,and the differences were statistically significant(χ2=5.008,4.397;7.142,4.688;4.407,5.189,all P<0.05).The 3-year cumulative survival rate of patients with low expression of miR-193a(30.43%)was lower than that of patients with high expression(60.32%)(χ2=17.861,P<0.001),while the 3-year cumulative survival rate of patients with high expression of miR-208b(27.14%)was lower than that of patients with low expression(64.52%)(χ2=16.340,P<0.001).The independent prognostic factors included serum levels of exosomes miR-193a(HR=0.493,95%CI:0.323～0.753)and miR-208b(HR=2.697,95%CI:1.382～5.262)(all P<0.05).Conclusion The preoperative serum miR-193a level in the exosomes was decreased and miR-208b level was increased,and their expression levels were related to the prognosis of patients undergoing GC radical gastrectomy.