In this paper, a two-dimensional waving plate as a fish-like body with unequal amplitude traveling wave motion that the maximum amplitude occurring at the tail in the wind is numerically simulated. We analyze the influence of the maximum amplitude, wavelength, and dimensionless wave velocity on the efficiency of energy extraction. Besides, we compare the unequal amplitude traveling wave motion with the equal one. The findings show that: when the wavelength is constant, the efficiency increases first and then decreases at a certain maximum amplitude with the increasing dimensionless wave velocity. When the dimensionless wave velocity is constant, the efficiency increases at a large wavelength with the increasing maximum amplitude while the efficiency increases first and then decreases at a small wavelength with the increasing maximum amplitude. When the maximum amplitude is constant, the efficiency increases first and then decreases at a certain dimensionless wave velocity with the increasing wavelength. In the same motion parameters, the efficiency of the equal amplitude traveling wave motion is higher than that of the unequal one with the maximum amplitude occurring at the tail.