Emissions of biomass fuel combustion in residential stove from Chinese countryside were analyzed to determine the endocrine disrupters by using recombinant yeast bioassay. The results showed that there were significant steroid modulating activities found in combustion soot of five kinds of biomass fuels, which were wood, crop residue, grass, bush and rice straw. The steroid activities in the different sub-fractions from chromatographic separation were also determined, and the results indicated that polar fraction extracted by methanol and aromatic fraction extracted by benzene had relatively high steroid activities, and aliphatic fraction almost had no activity. The GC/MS results showed that polycyclic aromatic compounds and their derivatives, substituted phenolic compounds and their derivatives, aromatic carbonyl compounds, and higher molecular weight alcohols and ketones may be the main steroid disrupters in these soots.