Objective To explore the clinical effects of postoperative restrict rehydration on different body mass index (BMI) of patients with colorectal cancer. Methods From January 2008 to January 2009, the patients diagnosed definitely as colorectal cancer were analyzed retrospectively. The postoperative early rehabilitations were studied and compared in different fluid therapy with different BMI (underweight group, normal group, overweight group).Results The first defecation time, aerofluxus time and ambulation time of the fluid restriction group were significantly earlier than those of the tradition therapy group (Plt;0.05), and postoperative in-hospital time was also less (Plt;0.05). However, the differences of early postoperative rehabilitation among underweight group, normal group and overweight group in the tradition therapy group and fluid restriction group had no statistical significance (Pgt;0.05). The complications such as pulmonary infection, anastomotic leakage, intestinal obstruction and wound dehiscence in the fluid restriction group were significantly lower than those in the tradition therapy group (Plt;0.05). In the tradition therapy group, the incidences of anastomotic leakage and wound dehiscence in overweight group were significantly higher than those in the underweight and normal group (Plt;0.05). The rate of postoperative complications among underweight group, normal group and overweight group in the fluid restriction group had no statistical significance (Pgt;0.05). Conclusion Postoperative restrict rehydration for overweight colorectal cancer patients has a good clinical effect, which can promote the early postoperative rehabilitation.