The collection and grain size analysis were carried out for sand dust sedimentation in Harbin, 20th March 2002. The result indicated that sand dust sedimentation gave priority to silt (4~8Φ), occupying 71.18%, sand composition (>4Φ) is 21.7% and clay composition (<8Φ)only 7.13% at Harbin. The granularity of sand dust sedimentation was the coarsest in the reports so far. The sedimentation granularity distribution was charactered by multi-peak states, coars sand silt of 4.85-5.10Φ grain grade composed first main peak, occupying about 7.4%, medium sand of 1-1.25Φ grain grade composed second main peak, occupying about 1,29%,and clay composition of 10.25-10.5Φ grain grade composed third main peak, occupying about 0.52%. The average grain diameters of sedimentation (Mz) was 5.14Φ, sorting coefficient, 1.81, Skewness, 0.044, and Kurtosis, 1.494, silt and clay ratios, 7.3. The granularity features shown that sand-dust sedimentation was admixture, derived from different sources both far distance and short distance, and coarse particle was near-sources material that was transmitted by low altitude airflow. The biology status and zoology environment of sand-dust sedimentation source area are relatively inclement. Nudity infield, wasteland and plain, river bed and floodplain fine alluvium, bareness lakes and dust of city earths surface and construction sites, and so on, may be material fountainhead. The keystone of weather projects for preventing sand-dust in Harbin should put to controlling sand-dust fountainhead around Harbin.