Abstract: Objective To establish a mouse model of cancer cachexia(CC) and explore its natural development process. Methods BALB/c male mice were inoculated with C26 in the armpit subcutaneously to build CC model.Thirty-two male BALB/c mice were randomly divided into normal control group(n=8), mild cachexia, moderate cachexia and severe cachexia groups(n=8, respectively).Rats in normal control group received right axillary subcutaneous single injection of 0.1 ml normal saline, and rats in cachexia group received right axillary subcutaneous single injection of colon adenocarcinoma cell line C26 cell suspension(0.1 ml, 1×10⁶).After modeling, the mental state, hair, activity, body weight, food intake, water volume, tumor weight and volume of the mice were observed.When the body weight of mice in mild cachexia group decreased 5%, moderate cachexia group decreased 10%, severe cachexia group decreased 15%(normal control group and severe cachexia group were sacrificed at the same time), blood tests including CBC, biochemical factors and inflammatory factors were performed.Mice in cachexia group were dissected to weigh the tumor. Results In normal control group, the general condition, food intake and water intake did not change significantly.The subcutaneous tumor nodules in cachexia group could be touched at day 5, and the tumor volume grew fastest at day 7-8.The body weight decreased 5% at day 9 with mild cachexia, decreased 10% at day 13 with moderate cachexia, and decreased 15% at day 18 with severe cachexia.The body weight, food intake, water intake were significantly lower in cachexia group than normal control group, and they decreased in a severity-dependent manner.The white blood cell count(WBC), neutrophil percentage(NEUT%), triglyceride(TG), cholesterol(CHO), IL-6, TNF-α and CRP significantly increased, while the percentage of lymphocytes(LYM%), total protein(TP), serum albumin(ALB) and blood glucose(GLU) decreased significantly in cachexia group, and they all changed in a severity-dependent manner. Conclusion Establishing mice model of cancer cachexia with subcutaneous inoculation of C26 cells shows high tumorigenic rate, good stability, and it also conforms to the physiological and pathological characteristics of cancer cachexia, which is a simple and valid method. As time passing, mice change from mild cachexia to moderate cachexia and then to severe cachexia with different degrees of malnutrition, inflammation and metabolic disorders.