Objective To evaluate the relationship between the characteristics of CT perfusion parameters and the degree of pathologic differentiation as well as TNM staging in rectal cancer. Methods 24 patents with histological verified rectal cancer underwent multi-slice spiral CT perfusion scanning before beginning therapy. Time density curves(TDC) were created from the region of interest (ROI) in the target vessels, lesions and normal rectal tissue adjacent to the lesion. The parameters of ROI were measured, such as blood flow(BF), blood volume(BV), mean transit time(MTT), vascular permeability surface area product(PS) and CT enhanced peak ,then determined TNM stages and the degree of tumor differentiation after surgery. The correlation between the parameters and the clinical and pathological factors above was studied. Results The rectal cancer tissue showed significantly higher BF, BV , PS and CT enhanced peak (P<0.05) and showed significantly shorter MTT (P<0.05) compared with those of normal tissue. BF in group of higher degree of differentiation was significantly higher than those in poorly differentiated tumor (P<0.05), the parameters were not associated with disease stage(P>0.05). Conclusion To a certain degree, Multi-slice spiral CT perfusion imaging can reflect the blood flow perfusion of the internal tumors, and CT perfusion parameters have a certain value for differentiation of rectal cancer and normal tissues as well as identification of different degree of pathological differentiation.