To observe the effect of long-term feeding marine collagen peptide on the incidence and development of the spontaneous tumor,Sprague-Dawley rats at the age of 4-week were divided into the control group and three experimental groups.Control rats were fed with standard rat diet and the MCP-treated rats were fed with 2.25%、4.5% and 9%(wt/wt) MCP throughout the lifespan.The results showed that the spontaneous tumor incidence of MCP-treated rats were obviously decreased compared with the control rats,with significance in the 9% MCP-treated female group and the 4.5% and 9% MCP-treated male groups;the long-term administration of MCP did not affect the palpable time and growth time of mammary gland tumor and the final volume of mammary gland tumor of the 2.25% and 4.5% MCP-treated groups were significantly decreased compared with the control group;the lifespan of tumor-bearing rats in the MCP-treated groups were prolonged,with significance in the 9% MCP-treated groups;compared to the control group,the incidence of death from tumors was decreased in MCP-treated groups in comparison with the control group of both sexes.In conclusion,the long-term administration of MCP might have some inhibitory effect on the incidence and the development of spontaneous tumor.