It is of great significance to clarify the influence mechanism, action path, and characteristic factors of urban blue and green space on residents’ mental health for building a healthy city and breaking through the urban mental health crisis.Firstly, we analyzed the domestic and foreign research on the impact of urban blue and green space on residents’ mental health in the past 20 years, sorted out their development situation, and identified research hotspots. Then, combined with the literature content, the promotion benefits of blue and green space on mental health promotion, promotion mechanism, and planning strategies of blue and green space for mental health promotion were reviewed in detail. The findings are as follows: (1) Related research is in the stage of rapid development and has great development potential in China; The research shows a multidisciplinary trend. Foreign research focuses on the quantification of health benefits and mechanism analysis, while domestic research advances both theory and practice. (2) Studies have confirmed that urban blue and green space has a positive effect on mental health. Improving mental recovery ability, reducing exposure to environmental hazards, promoting health behavior, and enhancing neighborhood satisfaction are the main action paths. Building an econometric model to identify the correlation between the two is the main research paradigm. (3) Studies have proposed strategies to optimize the mental health promotion effect of blue-green space from three aspects: green space quantity and accessibility, green space spatial pattern, landscape quality, and design level. (4) In the future, further research can be carried out from four aspects: refining research objects, deepening quantitative methods, expanding the research paradigm, and strengthening the transformation of results. It is expected to improve the understanding of the influence of urban blue and green space on mental health and provide a theoretical basis for the planning and design of promoting residents’ mental health.