Gastritis is inflammation of gastric mucosal and submucosa in response to acute and chronic injury which usually caused by Helicobacter pylori (H. pylori). Inflammation due to H. pylori will conduce Reactive oxygen species (ROS), a marker of pathogenesis and worsening of gastritis and gastric ulcer disease. ROS will increase the expression of Glutathione peroxidase (GPX), one of the endogenous antioxidants founded in mitochondria, cytosol and extracellular. The objective of this study was to evaluate level of GPX serum in gastritis patient with H. pylori and without H. pylori. This study used cross sectional study in 40 patients with gastritis at Haji Adam Malik General Hospital, Medan, North Sumatera. Diagnosis of gastritis based on inflammation of gastric mucosa in endoscopic, H. pylori infection was made if positive results of CLO test were found and level of GPX serum was determined by ELISA kit glutathione peroxidase paint R5505. Data were collected and analyzed using SPSS version 22. There was no significant association between level of GPX serum and gastritis patient with H. pylori infection