Experiment analyses were carried out on dustfall samples which were collected from three sampling points in Fengfeng District according to the changes of seasons. The results showed that the distributions of n-alkanes in dustfall can be mainly divided into two types with the CPI values ranging from 1. 54 to 10. 54,including behind peak type and dual distribution type. Both of them take C29 as main carbon. N-alkanes in dustfall mainly come from fossil combustion such as coal when in winter but come from bio-organic matter like higher plant and pollen in the other seasons. Source of bio-organic matter are gradually reduced from spring to winter,while fossil combustion sources are increased.