How do the characteristics of senior executives affect firm's ESG performance? Utilizing the data of the A-share listed firms in China spanning 2009 to 2021, this study examines the effect of CEO's green characteristics on ESG performance based on the Upper Echelon Theory. The results show a positive relationship between firm's ESG score and CEO's green educational or work experience. Mechanism analysis shows that CEO's green educational background enhances corporate environmental awareness; CEO's green work experience helps the firm to avoid environmental administrative punishment and improve corporate innovation, which will benefit corporate sustainability. This paper helps to understand the relationship among the CEO's green characteristics, the motivation for sustainability, and the ability to improve the firm's ESG.