Abstract: Using a quasi-geostrophic nonlinear barotropic vorticity equation,setting a stationary foroing wave along the southern boundary.and by means of four schemes,the nonlinear critical layer and exciting Kelvin cat's eyes on the layer are simulated.hence the affection of the stationary forcing for tropical belt on generation,maintaining and oscillation of substropical high is determined.It follows from the simulated results that in the nonlinear critical layer southern boundary forcing also excites a stream field of Kelvin cat's eyes,having the anticyclonic circulation with the planetary scale.Moving.strength and shape changing of the cat's eyes are similar to those of subtropical high in the summer.but the results obtained through a stationary forcing of the northern boundary differ greatly from the subtropical high in the summer.Thus.It is possible that Kelvin cat's eyes in the nonlinear critical layer excited by the southern boundary forcing is very important new physical mechanism for generation.maintaining and oscillation of substropical high.A physical mechanism to cross the nonlinear critical layer on the substropical belt for the quasi-stationary planetary waves is supposed.