Objective The nutritional status of gastric cancer patients based on the nutritional risk screening scale NRS 2002 were investigated and analyzed. Based on the results of high - throughput sequencing the biomarker related to cachexia were screened. Method 1134 patients with gastric cancer who were hospitalized in the First Affiliated Hospital of Air Force Military Medical University from December 2016 to December 2018 were selected as the study subjects. The nutritional status of patients was evaluated according to the NRS 2002. The correlation between nutritional status and demographic characteristics disease progression laboratory indicators and outcomes was compared. At the same time the blood of patients with cachexia n = 3 and non-cachexia n = 2 were extracted for full transcriptional genome sequencing and the differentially expressed miRNAs were screened as a predictive biomarker of cachexia in gastric cancer. Result 772 of the 1134 patients were malnourished and accounting for 68. 08% of the total number of patients. The incidence of malnutrition has differences in age smoking and drinking history tumor stage BMI laboratory indicators and short-term adverse outcomes. The incidence of malnutrition in elderly patients ≥60 years old was significantly higher than that in <60 years old non-elderly patients P= 0. 007 . Smoking P<0. 001 and drinking P= 0. 005 have a significant impact on the nutritional status of patients with gastric cancer. The nutritional status of gastric cancer patients worsened with the increase of tumor stage P = 0. 018 . The albumin hemoglobin and BMI of patients with malnutrition were significantly lower than those with good nutritional status while white blood cell count was higher. Multivariate Logistic regression analysis showed that malnutrition was an independent risk factor for poor prognosis in patients with gastric cancer. Furthermore plasma exosomal miR-206 was identified as a biomarker for the early diagnosis of cachexia via whole-gene sequencing to make up for the lack of methods for the early diagnosis of cachexia. Conclusion The incidence of malnutrition in gastric cancer patients is high and the nutritional status of gastric cancer patients is related to age smoking and drinking history tumor stage BMI laboratory indicators and other factors. Malnutrition is an independent risk factor for poor prognosis of gastric cancer patients. Furthermore we identified a novel plasma exosomal biomarker miR-206 for the early diagnosis of cachexia.