A new sample purification method was developed for the determination of low levels of DDTs in soils.The tested soil was extracted with a mixture of hexane-acetone(1∶1) by ultrasonic method.The soil extracts was purified with a patented four-channel purification chromatograph before analysis by gas chromatography with electron capture detector(GC/ECD).Effects of different column packs and elution solvents on recoveries of DDTs were investigated.The results showed that by using ultrasonic extraction，new mixed filling material for the chromatogram column and elution with dichloromethane-n-hexane(4∶1)，the recoveries of DDTs were between 83.5% and 90.3%，and the method detection limits were between 2.0 ng?g-1 and 5.4 ng?g-1，implying that the method can be used for the determination of low levels of DDTs in soils.In addition，the spiked recoveries of DDTs based on the ultrasonic extraction and Soxhlet extraction were compared under the optimal purification conditions.The results showed that the recovery of the Soxhlet extraction method is higher than that of the ultrasonic extraction method，but the the former need consume more time.