Objective To evaluate the clinical value of magnetic resonance diffusion weighted imaging (DWI)in T staging of rectal cancer.Methods Rectal cancer patients were accepted in our hospital from January 2015 to December 2015.Rectal cancer patients were examined with T2 weighted imaging (T2 WI)and magnetic resonance DWI and given preoperative T staging.The sensitivity,specificity and accuracy of T2 WI and T2 WI combined with DWI in the diagnosis of DWI staging of rectal cancer were compared,and the relationship between the apparent diffusion coefficient (ADC value)and T staging of rectal cancer was analyzed.Results The accurate rate of T2 WI in diagnosis was 65.22%(60 /92),T2 WI and DWI diagnosis accurate rate was 76.09% (70 /92).The two diagnostic methods of colorectal cancer T staging diagnosis accurate rate had no significant difference (χ2 =1.18,P >0.05). Patients with good prognosis (T2 and T3 a)ADC value were significantly higher than the patients with poor prognosis in patients with ADC (T3 b,T3 c and T4 ),and the differences were statistically significant (all P <0.05).Conclusion DWI can be used as a complementary sequence for the diagnosis of T staging of rectal cancer by T2 WI.It had better consistency with pathologic stage.The ADC value of the tumor showed a decreasing trend along with the progression of T staging of rectal cancer,and provided reliable reference information for the preoperative treatment plan.