The microbiome residing in the gastrointestinal tract,serving as the host's second genome,is closely linked to the intake of nutrient and the immune system's de-fense mechanism of hosts.Compared to terrestrial mammals,the gastrointestinal microbi-ome of marine mammal cetacean has received less attention.Several studies have dem-onstrated that the cetacean gastrointestinal microbiome is highly affected by factors such as diet and habitat environment.Currently,the primary approaches for these studies are high-throughput sequencing based on fecal samples.This review paper summarized and analyzed the research methodologies,community structure,functional characteristics,and regula-tory strategies of the cetacean gastrointestinal microbiome,and several potential avenues for future development were also proposed.