Abstract: Preoperative neoadjuvant chemoradiotherapy is a routine treatment for rectal cancer. It helps to reduce rectal cancer staging, improve anus preservation rate, reduce local recurrence and achieve complete response. Diffusion-weighted imaging (DWI) provides information of molecular function of tumor. It can be used to evaluate the effect of neoadjuvant chemoradiotherapy treatment for rectal cancer. The value of DWI in preoperative neoadjuvant chemotherapy of patients with rectal cancer including monitoring early stage of therapy effect, tumor remnants, clinical and pathological response, as well as its limitations are focused in this review.