Scanning electron microscopy equipped with energy dispersive X-ray detector (SEM-EDX) was used to study the atmospheric dust fall aerosols collected in Lhasa under the regular meteorological conditions in summer. The results offer the particles size, mineral composition and mineral morphology of the atmospheric dust fall in Lhasa. Morphologic observation of SEM reveals that the dust falls are mainly composed of clay silicate particles in the irregular flaky shape and a certain amount of such anthropologic and biological particles as soot and pollens. On the basis of EDX analyses of 149 particles and by using the developed elemental weight method, the authors classified the particles into six different categories, i.e., atmospheric particles mainly composed of “Si-rich" particles, “Ca-rich" particles, “Fe-rich" particles, “C-rich" particles (fly ash particles from coal and oil combustion), “K-rich" particles and “Zr-rich" particles. Statistics of the particle quantity show that silicates possess 52.4% of total particles. The silicate particles in the sample include much more felsic components than mafic (Fe-Mg-rich ) particles, and the felsic particles are mainly distributed in four subgroups, namely, “quartz group", “orthoclase group", “pyrophyllite and montmorillonite group" and “muscovite and illite group"， with the mafic particles mainly distributed in the “biotite and vermiculite group". “Ca-rich" particles were detected in 28.2% of the particles, and most of Ca components are “high-Ca" particles and exist as calcite (CaCO3). A study of the mixture state of Ca in atmospheric particles shows that particles with weight ratio of Ca, P(Ca), greater than 0.1 and 0.02possess 47.3% and 86.8%, respectively, and 26.5% of the particles are Ca-dominant particles with P (Ca) ≥0.65. Particles with Ca are concentrated in the radius range of <5 μm，and most of the Ca is internal mixture in silicate particles. Sufficient attention should be paid to fuel carbonaceous particles from vehicle exhaust in emission reduction and control. The mineral composition and morphology of atmospheric dust fall act as important criteria in identifying pollution sources.