In the era of digital economy, data have become a new factor of production that accelerates the cultivation and development of new quality productive forces. Using a sample of Chinese A-share listed private firms from 2010 to 2024, this study employs the FinBERT2 large language model to construct a measure of corporate data resource information disclosure and empirically examines its impact on the investment efficiency of private firms. The results show that data resource information disclosure significantly reduces inefficient investment and improves investment efficiency, and these findings remain robust across a series of robustness tests. The mechanism analysis indicates that data resource information disclosure enhances investment efficiency of private enterprises mainly by alleviating information asymmetry and mitigating agency problems. The heterogeneity analysis further shows that the positive effect of data resource information disclosure on investment efficiency is more pronounced among private firms operating in high-tech industries, smaller firms, firms with lower asset intensity, firms with higher levels of digital investment, and firms located in regions with higher levels of marketization. Further analysis suggests that the inhibitory effect of data resource information disclosure on inefficient investment contributes to improving the total factor productivity of private firms. These findings provide empirical evidence for understanding the economic consequences of data resources and related information disclosure, as well as the determinants of investment efficiency in private firms, and offer important policy implications for promoting the high-quality development of China’s private economy.