The directed motion of Brownian particles is generated by a travelling asym
metric potential. The asymptotic behaviour of the probability density of th
e particles at a long time is a solitary wave. The Brownian particles can w
ork against an external opposing force with high efficiency. The analytical
expressions of the solitary wave and the efficiency of the Brownian partic
les are obtained. The average velocity and the efficiency of the particles
depends strongly on the travelling speed and the asymmetry of the potential
.