The purpose of this paper is to summarize and analyze the current state trends and key issues in the study of depression in elderly patients with chronic diseases, and to provide clues for mental health interventions for patients with chronic diseases. Based on the health ecology model, it summarizes the status of depression prevalence in patients with chronic diseases, summarizes the influencing factors of depression in patients, and analyzes the health outcomes of depression on patients. Depression was found to be prevalent among patients with chronic diseases, especially among female patients with chronic co-morbidities from rural households and specific age groups. Behavioral styles, social status, and policy environment were all important factors influencing depressive mood. Depressed mood not only affects patients’ quality of life, but may also exacerbate the course of chronic diseases and increase the consumption of healthcare resources. Therefore, it is important to pay attention to the mental health of patients while focusing on the treatment of chronic diseases to reduce the multidimensional impact of depression on patients with chronic diseases.