【Abstract】Objective To study the predictive value of diffusionweighted imaging (DWI) combined with dynamic contrastenhanced MRI in response to neoadjuvant chemotherapy for rectal cancer before operation.Methods 76 patients with rectal cancer admitted to our hospital from January 2016 to January 2019 were selected. All patients underwent diffusionweighted imaging (DWI) and dynamic contrastenhanced magnetic resonance imaging (DCEMRI) and neoadjuvant radiotherapy and chemotherapy. After the end of chemotherapy, surgical intervention was performed. According to the pathological examination, the patients were divided into treatment response group and treatment nonresponse group. Postoperative pathological examination was graded as gold standard, and the changes of tumor regression rate, ADC value and quantitative hemodynamic parameters were analyzed.Results Before neoadjuvant radiotherapy and chemotherapy, the maximum diameter of tumor was (502±058) cm and the maximum diameter was (300±035) cm in 76 patients with rectal cancer. Seven days after neoadjuvant radiotherapy and chemotherapy, 76 patients were operated and resected, 53 patients were operated and pathological grade IIII as the treatment response group, 23 patients were treated and non response group. The tumor regression rate and ADC value of patients in the treatment response group were higher than those in the treatment non response group, and the quantitative hemodynamic parameters Ktrans, Kep and Ve were lower than those in the treatment non response group (P＜005). The results of logistic regression analysis showed that ADC, Ktrans, Kep and Ve were correlated with the response of rectal cancer (P＜005).Conclusion Diffusionweighted imaging combined with dynamic contrastenhanced MRI can effectively predict the response of patients with rectal cancer to neoadjuvant radiotherapy and chemotherapy before operation.