Nutrition is the foundation of cancer therapy and diet is the foundation of nutritional therapy. In the five-step nutrition therapy diet occupies the first and second steps and is the optimal method which characterized by high frequency variety affordability and universality. A reasonable diet can provide patient with sufficient and balanced nutrients which can improve the immunological function promoting the tolerance and continuity of cancer therapy. Food choices are a part of the elaborate behavior pattern which gradually formed under the influence of lifestyle habits culture society economy and environment. Dietary education needs to employ behavioral intervention strategies to help cancer patients master dietary knowledge change dietary behaviors and promote well-being. Cancer patients experience a significantly metabolic changes during different disease stages and treatment periods resulting in varying nutritional needs. Comprehensive and accurate dietary education can enable cancer patients to follow dietary plans that align with their metabolic characteristics and pathological changes solidifying the foundation of nutritional therapy in cancer. This article reviews the relevant theories implementation processes and specific content of dietary education for cancer patients providing reference and guidance for medical staff to conduct dietary education.