The analysis of particle size of street dusts in Xianyang City collected in April, 2008 indicates a bimodal dist ribution spect rum with the first mode being 35～75μm and the second, 280～500μm. The averaged particle size is found to be 80μm. The dist ribution is characterized by wide kurtosis, better symmetry, and better sorting, which is similar to the particle size distribution of loess and modern duststorms. This indicates that street dusts are a mixture of coarse particles derived from local area and fine particles transported over a long distance by aeolian agent. Under the proper aerodynamic conditions, 56.7 % of street dust particles can be picked up and transported by suspension.