Pectoral fin propulsion bionic fish has the characteristics of high mobility and flexibility, but pectoral fin modeling has always been a great challenge because the pectoral fin dynamics is a strongly nonlinear. In this paper, the three-dimensional kinematic model of the pectoral with three fins is established by imitating the motion mode of real organisms, and the hydrodynamic model of the pectoral fin is provided by using Morrison equation, and finally the effects of three parameters of pectoral fin motion frequency, amplitude and transmission wavelength on thrust are analyzed by simulation. The intrinsic properties of the pectoral fin to produce propulsion force are revealed: that is, when the ratio of propulsion wave velocity to swimming speed is less than 1, negative thrust is generated, and positive thrust is generated when it is greater than 1. These results are of great significance for guiding the development of the prototype.