Abstract: A sample pretreatment method of microwaveassisted extractionFlorisil solid phase extraction cleanup for gas chromatographic (GC) and gas chromatographymass spectrometric (GC-MS) determination of the trace semivolatile organochlorine pesticides in soils was developed. The microwaveassisted extraction and Florisil solid phase extraction conditions were optimized. Under the optimum condition, the recoveries of 18 organochlorine pesticides (α-HCH, β-HCH, γ-HCH, δ-HCH, heptachlor, aldrin, heptachlor epoxide, endosulfan Ⅰ, p,p′-DDE, dieldrin, endrin, endosulfan Ⅱ, p,p′-DDD, o,p′-DDT, endrin aldehyde, endosulfan sulfate, p,p′-DDT, methoxychlor) were 89.56%～114.22%. The instrument detection limit, recovery, precision and detection limit of method were compared between GC and GC-MS. Based on the combination of sample pretreatment method with GC (for quantitative determination) and GC-MS (for qualitative determination) determination, an analytical system for the determination of 18 organochlorine pesticides in soils was established and has been applied to the determination of organochlorine pesticides in soil samples with satisfactory results.