Abstract Background To study on expressions and clinical significances of CD133 protein and CD133 mRNA in primary lesion of gastric adenocarcinoma (GC). Methods Expressions of CD133 protein by immunostaining (99 cases) and CD133 mRNA by semi-quantitative RT-PCR (31 cases) were detected in primary lesion and in noncancerous gastric mucosa tissue (NCGT). Correlations of CD133 protein expression with clinicopathological parameters and post-operative survival were analyzed. Relations of CD133 mRNA level with Ki-67 labeling index (LI), and lymphatic metastasis were assessed too. Results Brown particles indicating CD133 protein positivity occurred in some parts of tumor cells and epithelium. Expressive percentage of CD133 protein positivity was significantly higher in subgroups with >5 cm diameter (P = 0.041), later TNM stage (P = 0.044), severer lymph node metastasis (P = 0.017), occurrences of lymphatic invasion (P = 0.000) and vascular invasion (P = 0.000) respectively. Severer invasion depth (P = 0.011), lymph node metastasis occurrence (P = 0.043) and later TNM stage (P = 0.049) were the independent risk factors for CD133 protein expression. Average brightness scale value (BSV) of CD133 mRNA was significantly higher in subgroups with >5 cm diameter (P = 0.041), lymph node metastasis occurrence (P = 0.004) and in lower Ki-67 LI (P = 0.02). Relative analysis revealed that BSV of CD133 mRNA related positively to metastatic lymphatic nodes ratio (P = 0.008) and metastatic lymph node number (P = 0.009), but negatively to Ki-67 LI (P = 0.009). Survival of positive subgroup of CD 133 protein was significantly poorer (P = 0.047). Lymph node metastasis occurrence (P = 0.042), later TNM stage (P = 0.046) and CD 133 protein positive expression (P = 0.046) were respectively the independent risk factors to survival. Conclusion Higher expressive level of CD133 mRNA is associated to lower Ki-67 LI and severer lymphatic metastasis. Therefore, the expressive level of CD133 mRNA can play an appropriate role to reflect the status of lymph node metastasis and proliferation of GC. CD133 protein expression is closely related with larger tumor, later TNM stage, lymphtic metastasis and survival of GC.