Loss carryforward is a crucial instrument for tax macro-regulation since it functions as a tax mechanism to balance the tax system’s asymmetric treatment of gains and losses. Since 2018, the time restriction for loss offsetting tax has been greatly loosened, and the loss carryforward term for high-tech enterprises has been increased from 5 to 10 years. This study uses the data of listed A-share firms in Shanghai and Shenzhen from 2013 to 2022 as a sample to investigate the effects of the prolonged loss carryforward years on high-tech enterprises’ investment efficiency and its mechanism of action. According to the findings, the extension of loss carryforward years has a significant effect on the investment efficiency of high-tech enterprises. Further research results indicate that the extension of the loss carryforward period to improve investment efficiency is only significant in enterprises with sufficient investment opportunities, large strategic differences and growth period, which confirms that the policy of extending the loss carryforward period has the efficacy of resource allocation, and indicates that good development potential and high risk characteristics are two important factors for the extension of the loss carryforward period to stimulate the improvement of the investment efficiency of hi-tech enterprises. In addition, this paper also finds that enterprise risk-taking is an important channel mechanism through which loss carryforward extension affects investment efficiency. This paper systematically examines the policy effect of loss carryforward year extension policy in promoting the investment efficiency of high-tech enterprises, provides evidence support for the resource allocation role of government tax policy as a market-oriented means, and has reference value for the improvement of tax policy.