Under the background of the "Digital China" strategy, in-depth exploration of the impact of digital network usage on the mental health of the elderly is of profound significance for alleviating the mental health crisis among the elderly and promoting healthy aging. Based on the 2020 China Elderly Social Tracking Survey Data (CLASS), an empirical study examined the impact of digital network usage on the mental health of the elderly, and conducted heterogeneity analysis and impact mechanism tests. The research results show: (1) Digital network usage helps to reduce the depression score of the elderly, improve the episodic memory score and mental state score. This conclusion still holds after conducting endogeneity handling and robustness tests. (2) Heterogeneity analysis indicates that digital network usage has a more significant positive effect on the mental health improvement of middle-aged and elderly people (aged 70 and above), non-singletons, and those with certain self-care abilities. (3) In addition to the direct effect, digital network usage also indirectly affects the mental health of the elderly by improving the self-aging attitude of the elderly group and enhancing their social adaptation level. Based on this, this paper believes that the digital literacy of the elderly group should be enhanced, attention should be paid to the digital integration of disadvantaged elderly groups, and special attention should be paid to the positive effects of digital networks on the mental health of the elderly.