The evaluation of public policies has been a long-standing concern for both the government and academia. However, most studies either focus on the effectiveness of the text or the outcomes rarely examining the complete chain from policy effectiveness to policy outcomes. This paper, based on the "dual effectiveness" mixed method, takes China's science popularization as an example, and uses panel data from 31 provinces from 2012 to 2022 to conduct empirical analysis, systematically investigating impact of policy effectiveness on policy outcomes and its mechanism. The study finds that policy effectiveness has a significant impact on policy outcomes; the level of policy effectiveness and outcomes significantly depending on the target audience, with the highest performance seen in incentive policies, followed by protective policies, and the weakest in environmental policies; among the four dimensions policy, policy measures have the greatest impact on the effectiveness of policy implementation, followed by policy feedback and policy goals. Therefore, the government should further strengthen the driving of incentive policies, improve the efficiency of incentive policy supply through revision of incentive measures. And improve the overall effectiveness and outcome of the policy by enhancing policy measures, goals, policy strength, and policy feedback. The marginal contributions of this paper are as follows:(1) By adopting a "dual-effect" mixed method, it first quantitatively measures the effectiveness of popular science policies, then analyzes the impact of policy effectiveness on policy outcomes, providing a more objective measurement of the validity of policy texts and their influence on actual implementation outcomes;(2) Starting from multiple factors influencing policy implementation outcomes, it comprehensively considers the impact of policy effectiveness, different categories of policy effectiveness, and various policy dimensions on policy execution results, in order to avoid one-sidedness and subjectivity in policy performance evaluation;(3) Using the established policy effectiveness evaluation model as a tool, a more accurate assessment of the implementation effects of different policy documents and policy instruments can be conducted.