To Evaluate the Efficacy and Safety of Vitamin B12 Contains Extract of Lamb's Stomach in Treatment of Chronic Atrophic Gastritis (CAG)

Inclusion Criteria: * Age 18-70 years, male or female * Histologically diagnosed CAG * HP negative confirmed by gastric mucosal staining * Signed an written informed consent Exclusion Criteria: * CAG with high-grade intraepithelial neoplasia * Severe gastric mucosal erosion or bleeding needing treatment * Active peptic ulcer, GERD, or esophageal stricture * History of upper GI tract surgery * History of malignant diseases * With depression, anxiety neuroses, or hysteria * Heart failure (NYHA class lll or lV), liver disease (ALT ≥ 80 IU/L, AST ≥ 80 IU/L) or renal disease(Cr ≥ 150 ummol/L) * Uncontrolled hypertension * Uncontrolled diabetes * Alcohol abuse * Drug allergy * Participated in another investigational study within 4 weeks prior to Visit 0 * Pregnancy, be a nursing mother or without conception control * There is any concern by the investigator regarding the safe participation of the participant in the study or for any other reason; the investigator considers the participant inappropriate for participation in the study