This paper investigates the spectra of fusion α-particle leaking out from the plasma boundary in a Tokamak fusion reactor, bombarding the first wall. The loss mechanisms of α-particle were studied, and the slowing down-diffusion equations describing the α-particle transport in plasma were set up. The contributions from banana-trapped particles, transit panicles and superbanana ripple trapped particles to the diffusion coefficient were included in the study. The equations were numerically solved for Tokamak reactors with typical parameters to obtain the required α-particle spectra. The physical significance of the results is discussed finally.