Abstract: The basic structure and working principle of biomimetic fish fin is briefly introduced.Then,the tip deformation error of the shape memory alloy(SMA) plate pair used as fin actuators is computed theoretically to improve the deformation precision of the SMA biomimetic fish fin.The relationship between the non-dimensional drag coefficient of SMA plate surface and time is presented,and the pressure distribution on and around the SMA plate surface as well as the Karman vortex configuration in the wake at a certain time are given.Finally,an experiment is carried out to verify the theoretical results.