Inspired by some batoid fishes using horizontal trigonal pectoral fin for propulsion or maneuverability, a micro flexible mimetic propulsor actuated by shape memory alloy (SMA) wires is presented. Firstly, based on the motion characters of the pectoral fin of manta ray, a simplified kinematics model was set up. Secondly, a three-dimensional numerical simulation on the oscillatory fin was performed by computational fluid dynamic (CFD) to investigate the interaction with the surrounding fluid and the propulsive force production. Thirdly, action experiment of the propulsor is done to verify the concept. At last, the propulsive performance of the propulsor is evaluated through thrust force measurement experiments. The experimental results accord with the CFD results well. The propulsor have potential feasibility applying in automatic underwater vehicles (AUV).