An observation on the interaction between marine mammal and krill midwater trawl was carried out onboard the Chinese krill fishing vessel Fu Rong Hai during the 2018/19 fishing season. The underwater and on sea surface observations were both deployed. Although large numbers of Antarctic fur seal Arctocephalus gazella were observed around the vessel during the vessel fishing in the Subarea 48.3, no identified marine mammal was observed in the main body of trawl net. There was no marine mammal by-catch observed either. The observation found the Antarctic fur seals would be attracted by the codend of krill trawl net, especially during the periods difficult to get foods. The observation also indirectly implied that well designed seal escaping devices might reduce the risk of accidently by-catch of Antarctic fur seals. Future researches on the interaction between marine mammals and krill fishing gears would be helpful to understand the relationships between krill fishing and krill predators.