Data assets serve functions such as value preservation and appreciation, financing, and value creation. They contain extensive information about enterprises’ operational status and future development prospects, providing significant references for external investors’ decision-making and greatly impacting the information efficiency in capital market. This study examines the correlation between data assetization and capital market information efficiency, along with the mechanisms and influencing factors involved. We select a sample of Chinese Hidden Champion small and medium-sized enterprises (SMEs) from 2011 to 2021, utilize text analysis methods to build a data assets dictionary, and extract keywords from corporate annual reports to depict the level of data assetization. The research results indicate that data assetization significantly enhances the information efficiency of capital market, specifically reducing stock price synchronicity and stock price delay. By categorizing data assets into own-use data assets and transactional data assets, we find that both types can improve the information efficiency of the capital market. Mechanism analysis reveals that enterprise data assetization can enhance the information efficiency of capital market by alleviating corporate financing constraints and improving forward-looking information disclosure. Factors analysis demonstrates that digital infrastructure and data circulation transactions can strengthen the enhancement effect of data assetization on the information efficiency of capital market. This study enriches the research outcomes in the micro-research field of data assets, providing valuable insights for promoting the digital transformation of Hidden Champion SMEs and the high-quality development of capital market.