A firm’s sustainable technological innovation (STI) is an important strategy to cope with the global challenges of the climate emergency and resource constraints. To encourage firms to pursue sustainable innovation, the government put its efforts into designing a proper environmental policy (EP). According to Porter’s hypothesis, a well-designed and flexible EP will advance the pace of a firm’s innovation. This paper argues that a flexible EP portfolio combining market and non-market-based EP instruments may affect a firm’s STI. Market-based EP instruments are cost-effective and consistent from a long-term view, whereas non-market-based EP instruments are more forceful and effective in the short term. Hence, these two kinds of EP instruments could complement each other. Furthermore, technical executives in top management teams will moderate the relationships between EP instruments and firms’ STI. Data analysis results of 618 Chinese public firms, who constantly participated in R&D activities during 2015–2019, supported these hypotheses. Contributions to EP and firm innovation theory, as well as suggestions for policymakers and firms’ top management teams, are discussed.