Objective · To investigate the level of lactamase β (LACTB) in gastric cancer and its influence on the prognosis of gastric cancer patients. Methods · The varied of LACTB in 90 pairs of gastric cancer tissue and peritumor tissue was analyzedimmunohistochemistry. The prognostic role of LACTB mRNA in gastric cancer was analyzedthe Kaplan-Meier Plotter database. The factors affecting the overall survival of gastric cancer patients were analyzed with Cox survival model. The prognostic nomogram model was established to predict overall survival of gastric cancer patients. The proteins which interacted with LACTB were analyzedthe STRING database, and they were taggedthe noassociated functional cluster of GO (gene ontology) and KEGG (Kyoto encyclopedia of genes and genomes) pathway. Results · The of LACTB in gastric cancer tissue was obviously lower than that in peritumor tissue (P0.000). The low of LACTB mRNA may suggest that the prognosis of gastric cancer patient is poor, and the C-index of nomogram for predicting prognosis of gastric cancer patients was 0.641. A set of LACTB and 38 proteins which interacted with LACTB participated in five kinds of signaling pathway. Results for the classification of GO (gene ontology) annotation demonstrated that the proteins were involved in one kind of cellular component, nine kinds of molecular function and two kinds of biological process. Conclusion · The low of LACTB may be a poor-prognostic factor in gastric cancer.