Influence of aging on the extractability and bioavailability of HCHs (alpha-, beta, gamma- and delta- isomers) in paddy soil were investigated in the lab under simulated circumstances. Results indicate that extractable HCHs decreased as their contact time with soil increased. The aging rate of HCHs in soil was rather high at the initial stage, and then slowed down in the rest of the time. During the first 60 days aging period, alpha-HCH, beta-HCH, gamma-HCH and delta-HCH dropped off 57.2%, 50%, 52.2% and 43.2% of the initial concentrations, about 90.5%, 87.4%, 72.4% and 84.4% of the total quantity of HCHs decreased in 180 d respectively due to high aging rate. Bioaccumulation of HCHs in earthworm displayed the same rule as aging, that is, the contents of HCHs in earthworm decreased as the incubation time extended, and so did bioaccumulation factors (BAF). The contents of HCHs accumulated in earthworm showing the order of alpha-HCH > beta-HCH > delta-HCH > gamma-HCH, while the accumulative ability expressing the rule of gamma-HCH > alpha-HCH > beta-HCH > delta-HCH in the first 15 d, and then alpha-HCH > beta-HCH > gamma-HCH > delta-HCH in the rest incubation time. Though the extractable HCHs decreased with aging, they still can be accumulated in earthworms, thus posing potential risk to soil environment.