Abstract: Two different soils,black earth and brown earth,were chosen as test samples to prepare soils contaminated with DDT and its homologues (including p,p′-DDT,o,p′-DDT, p,p′-DDD and p,p′-DDE) at different concentration levels (using the brown earth samples) and different particle sizes (using the black earth samples).Thermal desorption technology was used to study the total removal rates of DDTs and removal rates of DDT and its homologues in the contaminated soils at 300 ℃ and five levels of residue time (10,20,30,40 and 50 min).The results showed that there were no significant differences between the removal rates of DDTs in soils with different pollution levels; the w(DDTs) were 290.17,498.69 and 718.69 mg/kg.Also,the pollution level had little influence on the removal rates of the four DDTs and their homologues.However,the results suggested that particle size (three levels:0.25-<0.85 mm,0.15-<0.25 mm,＜0.15 mm) had considerable impact on the DDT removal rates.The larger the soil particle sizes were,the more DDTs were desorbed.The results of one-way ANOVA testing further indicated that desorption and transformation efficiency of p,p′-DDT and p,p′-DDE largely hinged on soil particle size.