The chemical characteristics of a floating dust event in April 2000 over Beijing were analyzed based on observation data. The total mass concentration of 20 elements in floating dust period was 181.49 μg/m3, which is much smaller than that in dust storm with the same measurement and analysis method, bigger than that in non-dust period in Mar 1999. The size distributions of Al, Fe, K, Ca, Si, Ti, Mn were changed after the passage of floating dust, which may imply a new accumulation of atmospheric particles. The contributions of remote sources to coarse and fine particles in this case were 82.8% and 34.5%, respectively.