Social network cognition of the elderly has become a common consensus in the international community to actively deal with the aging population. Previous studies focused on the impact of social network cognition on the dietary diversity and self-rated health of the elderly, but ignored the possible interaction between them. Based on the CLHLS data of the health and longevity follow-up survey of the elderly in China, this paper uses fixed effect model and fixed effect model to analyze and verify the interaction between them. On the premise of controlling the related variables, the model shows that there is a significant causal relationship between the self-rated health of dietary diversity and social network cognition of the elderly. The elderly with good self-rated health of dietary diversity have a 22.0%-40.1% higher incidence of social network cognition than those with poor self-rated health of dietary diversity; Compared with the elderly without social network cognition, the elderly with social network cognition had 16.4%-25.6% higher rate of self-rated health; The study also found that social network cognition is more likely to play a significant role in the self-rated healthy samples of dietary diversity in the base period.