The invention discloses a single ball valve type motorcycle fuel steam collecting system, which comprises an oil tank, a steam collecting tube, an anti-roll valve and a carbon tank, and is characterized in that: the anti-roll valve is arranged inside the oil tank and fixed on the top of the oil tank; an air inlet is formed at the front end of the anti-roll valve; the rear end of the valve is fixedly connected to the front end of the steam collecting tube and is communicated with the steam collecting tube; the anti-roll valve comprises a top plate and a V-shaped bottom plate structure which consists of two oppositely arranged inclined panels; a rolling ball is arranged at the bottom of the bottom plate; a sealing ring is arranged on the left and right sides of the rolling ball respectively; the sealing rings are vertically fixed on a corresponding inclined panel at the bottom respectively; and an air hole is formed at the rear end of the anti-roll valve close to the top plate. The single ball valve type motorcycle fuel steam collecting system has the advantages of preventing fuel from flowing into the fuel steam collecting tube and guaranteeing the normal collection of fuel steam by the collecting tube and normal adsorption effect of the carbon tank, along with simple structure, low cost, reliable work and long service life.