This paper investigates the impact of changes in the officials’ performance evaluation system on ecological environment quality, as well as the effect of ecological improvements on officials’ promotion prospects. Analyses are conducted using the changes in the officials’ evaluation mechanism in China’s ecological function counties in 2013 as a quasi-natural experiment, incorporating a newly developed set of county-level comprehensive ecological environment index data and manually collated data on county leaders. Multiple methods are employed to address issues such as sample selection bias, reverse causality, and heterogeneity of treatment effects. The empirical analysis shows that the adjustment of officials’ performance evaluation indicators contributes to the improvement of ecological environment quality. This effect is more pronounced in regions where GDP evaluation is abolished, regions with lower economic development but better ecological environment foundations, regions closer to provincial capitals, and officials with shorter tenure, younger age, and male gender. The rationale behind this policy is that post-reform improvements in the ecological environment will increase the promotion prospects of officials in ecological function counties, enable these areas to secure additional ecological transfer payments, thereby enhancing their capacity for environmental expenditure, and establish a credible commitment mechanism for central-local contracts. This study not only examines the relationships between political incentives for officials and environmental protection, but also enriches the literature on environmental decentralization, multi-target governance, and environmental political economy.