The invention discloses a screening method of a non-invasive gastric cancer saliva biomarker. The screening method specifically comprises the following steps: protein sample preparation, protein quantification, proteolysis and freeze-drying, labeling a sample by iTRAQ, C18 desalting, liquid-phase separation and mass spectrum identification, and data analysis; the GO function enrichment including biology progress, the molecule function and the cell component is performed on the screened differential protein by using the Panther Classification System in the data analysis; and then the protein mutual effect analysis is performed on the differential protein by using the STRING analysis software; and then the KEGG signal path analysis is performed on the differential protein. Through the screening method disclosed by the invention, the specificity protein marker in the gastric cancer can be discovered through a fast and reliable proteomics technical program, thereby establishing a non-invasive, simple and convenient, fast and practical detection evaluation measure for the early diagnosis, the postoperative recurrence, metastasis, and prognosis observation of the gastric cancer.