Objective To study ultrastructure and clinical significance of gastrin secretory granule in colorectal carcinoma cells. Methods The gastrin expression in colorectal carcinoma tissue and blood of 10 cases was examined by using radioimmunity analysis and immunohistochemistry. The ultrastructure of gastrin secretory granule of 10 cases, the positive of gastrin immunohistochemistry of colorectal carcinoma were examined by using immunoelectron microscopic technique. Results The gastrin concentration of the colorectal cancer group 〔（130.75 ±21.34） pg/ml〕 was significantly higher than that of control group 〔（95.63± 12.26） pg/ml〕，Plt;0.05. In 10 specimens of colorectal cancer, 5 cases were gastrin immunohistochemistry positive (+++), 4 moderate positive (++) and 1 weak positive (+). Cells in colorectal cancer were polyshaped, with unusual nucleoli different in size, concentrating on the edge, the cytoplasm mitochondrion was plentiful with vacuolates, and more secretion granules could be seen, 400-1500 nm in diameter with a clear border of membrane. There were two types of granular appearance: type A was largest in bulk size, low electrodensity was welldistributed, granular core appeared loose; type B was smaller in bulk size, high electrodensity was welldistributed, nucleus was usually compact.protein A gold (pAg) positive granules were located partially in secreting granules. pAg positive granules in highly differentiated cancer were mainly located in secreting granules of type A. pAg positive granules in low differentiated cancer were mainly located in secreting granules of type B. A part of cancer cell membrane, and inside and outside of microvillus membrane, adhering to pAg granules in line could be seen. Conclusion The colorectal carcinoma cells may synthesize and secrete gastrin themselves, which may be the mechanism of high gastrin levels in colorectal cancer. The use of gastrin antagonist and receptor antagonist may treat the patents with colorectal carcinoma.