Abstract: Objective Meta-analysis was conducted to investigate the effect of methylene blue on the number of lymph node harvest in pathological specimens of gastrointestinal malignant tumors.Methods We electronically searched PubMed，EmBase，Cochrane Library，CBM，CNKI and Wanfang database for collecting the relevant studies about the detection of methylene blue and lymph nodes in gastrointestinal malignancies（from inception to December 2018）.Two researchers screened of the literatures according to the inclusion and exclusion criteria，and further extracted the data and evaluated the quality.RevMan 5.3 software was used for this analysis.Results A total of 21 articles（containing 22 independent data），including 1140 patients in the traditional mode group and 1098 patients in the methylene blue staining group，were included in the metaanalysis.The results of the analysis showed that the use of methylene blue tracer in gastrointestinal tumor specimens significantly increased the number of lymph node harvest（P<0.001）compared with conventional manual harvest of lymph nodes.Subgroup analysis suggested that the number of lymph nodes detected during the increase in methylene blue was not associated with cancer types and whether patients received neoadjuvant chemotherapy（P<0.001，respectively）.Conclusion Methylene blue staining can significantly increase the average number of lymph node harvest in tissue samples from patients with gastrointestinal malignancies，and exhibits potential clinical application value.

Key words: methylene blue, gastrointestinal cancer, lymph nodes harvest, neoadjuvant chemotherapy, Meta-analysis