Abstract: Thermal management of optical module interconnected system is crucial for achieving cloud computing and 5G networks, but current research in this area remains relatively scarce. The current heat dissipation of optical module interconnected systems mainly relies on heat sinks and fans. With the widespread deployment of high-speed optical modules above 400 Gbit/s, the heat dissipation problem of optical module interconnected systems has also received more attention and faces greater challenges. The quad small form-factor pluggable-double density (QSFP-DD) optical module interconnected system is taken as the research object of this paper. A thermal model of the QSFP-DD optical module interconnected system is established. The effects of ventilation grille free area ratio (FAR), fin height and quantity of heat sink on the heat transfer performance of the QSFP-DD interconnected system are studied through numerical simulations. The research results indicate that by optimizing the matching relationship between fin height, fin quantity of the heat sink and the system flow resistance, the heat transfer efficiency of optical interconnected systems can be significantly improved. This research achievement provides important theoretical basis and engineering guidance for thermal design of optical module interconnected systems.