The study aims to explore the synergic benefits of reducing air pollutants and CO₂ and water consumption under the carbon emission peak (CEP) policies at a city level. Air pollutants and CO₂ emissions are predicted by the Low Emissions Analysis Platform (LEAP) model, and the water consumption is forecast by the quota method. Two scenarios are constructed with the same policies, but to different degrees: the reference scenario achieves CEP in 2030, and the green and low carbon scenario achieves CEP in 2025. The prediction results show that air pollutant emissions, CO₂ emissions, and water consumption can be obviously decreased by intensifying the CEP policies. The synergic abatement effect was illustrated by the synergic reduction curve. Accelerating the adjustment of economic structure saves the most water, reduces the greatest amount of CO₂ emission, and also obtains the best synergic reduction capability between water consumption and CO₂ emission. Transforming the traditionally long process of steelmaking toward a short electric process reduces the majority of PM_2.5, SO₂, and VOC emissions, while consuming more water. The study provides a new viewpoint to assess and optimize the CEP action plan at city levels.