To differentiate between natural and anthropogenic particulate sources in the atmosphere in Lanzhou City, samples were collected in different sites. The dust flux was calculated and magnetic measurements were conducted. Results show a distinct patt of variation of dust flux within a year and it agrees with the shifts of atmospheric circulation regime. The magnetic parameters indicate that natural sources are the major components of atmospheric particulate during late spring and early summer,while anthropogenic sources contribute much more during winter months. The data also support the earlier findings that magnetic parameters are effective for differentiating between particulate arising from natural sources such as soil erosion and from anthropogenic sources such as coal combustion.