Abstract:  To evaluate the dosimetric characters of different three-dimensional conformal radiation therapy ( 3DCRT ) techniques for early stage primary gastric lymphoma treatment and provide a reference for its optimized clinical application. Methods: Nine patients with early stage primary gastric lymphoma were enrolled for the current research. A simulated CT position was made in the fasting state. Gastric tumors with invaded lymph nodes, clinical target volume, and planning target volume ( PTV ) were contoured on each computed tomography scan. Organs at risk ( OARs ), such as each kidney, the liver, and the spinal cord were also contoured. Treatment planning for the ordinary four-field 3DCRT and optimized six-field 3DCRT was conducted for each patient. The prescribed PTV dose was 36 Gy. The dose distribution of PTVs and OARs were compared using the dose-volume relationship line graph. Results: The conformal indices for the ordinary four-field 3DCRT and optimized six-field 3DCRT were 0.67 ± 0.06 and 0.64 ± 0.05, respectively, whereas the inhomogeneity indices were 1.10 ± 0.02 and 1.11 ± 0.03, respectively. The V15 ( ratio of the kidney volume accepted higher than 15 Gy irradiation ) values for the left and right kidneys in the ordinary four-field 3DCRT and optimized six-field 3DCRT were 47% ± 30%, 33% ± 18%, and 24% ± 18%, and 12% ± 12%, respectively. The V20 ( ratio of the liver volume accepted higher than 20 Gy irradiation ) values for the liver in the optimized six-field 3DCRT decreased by 24% compared with those of the ordinary four-field 3DCRT. Conclusion: 3DCRT can successfully achieve the ideal dose distribution and coverage over the target volume, and the optimized six-field 3DCRT can better protect the kidneys, liver, and other OARs.