Under the context of productivity-oriented development, this study investigates whether the accountability system for business and investment activities, as an external governance mechanism, can improve the operating efficiency of state-owned enterprises (SOEs). Using a sample of A-share listed firms in Shanghai and Shenzhen from 2013 to 2023, we examine the impact of this accountability system on SOEs' high-quality development. The results show that the implementation of the accountability system significantly enhances SOEs' high-quality development, as reflected by higher total factor productivity. Further analyses reveal that the accountability system improves productivity by promoting high-quality innovation, strengthening internal control, enhancing investment decision-making prudence, and improving investment efficiency. The effects are more pronounced among SOEs with heavier social burdens, those in the growth or mature stages, firms with weaker Party organization governance, and firms located in regions with less developed legal environments. In addition, based on novel measures constructed with large language models, we find that the accountability system also strengthens firms'market power. Overall, this study highlights the economic consequences of accountability-based governance and extends research on institutional constraints and SOE development. The findings also offer implications for improving the supervision framework of state-owned assets in China.