Abstract: In order to obtain the characteristics of particle size and to determine its main sources of street dust in Xuchang city, Street dust samples collected on March, 2012 were analyzed by Mastersizer 2000 Laser Grainsize Analyzer. Results showed that: Xuchang street dust were mainly silt, followed by sand and clay, and displayed an three peaks and sharp frequency curve, the first mode was 30~145 μm, second model was 4~15 μm, third one was 0.5~1 μm, the average particle size were range from 25.42 to 236.15 μm, poor sorting and negative datum of skewness. Size distribution of Xuchang City street dust were similar to modern storm particle size patterns, which indicated that Xuchang City street dust deposition was the continuation of wind deposition, namely street dust was a mixture of coarse particles that transported by monsoon circulation and fine particles that controlled by westerly circulation, Moreover, coarse particles from the building site led samples that collected nearby to have larger particle size, which reflected the contribution of construction to street dust.