As the importance of science and technology innovation rises in global competition, taking the BRICS expansion as an opportunity, deepening the science and technology (S&T) innovation cooperation among BRICS countries is of great and far-reaching significance to reshape the world’s scientific and technological governance pattern and enhance the discourse power of the countries in the “Global South”. Based on the data of BRICS countries' thesis cooperation from 2000 to 2023, the article analyzes the topology and centrality of BRICS S&T innovation cooperation network from the perspective of dynamic evolution, adopting social network analysis and geographic detector, and examines the influence of multi-dimensional proximity and interaction on the evolution of S&T innovation cooperation network in each stage and the mechanism of the influence. The results show that: (1) during the study period, the scale of BRICS science and technology innovation cooperation network has been enlarged, the cooperation links between the subjects have been gradually increased, the network density has shown a trend of growth followed by a slow decline and remained stable, there is a trend of intensive cooperation and cluster development within the innovation network, the important centers of the innovation subjects have gradually come to the fore, and the topology of the network has gradually developed and matured, and it is in the transitional period of the stochastic network evolving into a scalar-free network. (2) Important center nodes of the cooperation network have come to the fore, exerting important influence and radiation-driven ability; at the same time, the ranking of key intermediary nodes is relatively stable, playing the role of intermediary bridge communication. China is in the core position of leading and spearheading in the BRICS S&T innovation cooperation network, with greater influence. (3) Multi-dimensional proximity factors play different degrees of positive influence in the network, R&D investment proximity is the dominant factor affecting innovation cooperation in the study period, with the highest explanatory power; the influence of geographical proximity gradually decreases and tends to be stable with the advancement of time; and there is a two-factor enhancement interaction between different proximity factors, with different degrees of enhancement effect.