In order to understand the contents, spatial distribution and sources of medium-chain chlorinated paraffins (MCCPs) in the soils from Chongming Island, the concentrations of MCCPs in 27 soil samples were analyzed by GC-ECNI-MS. The total concentrations of MCCP8 (sigma MCCPs) in all samples ranged from 2.56-96.3 ng x g(-1), with a median of 7.32 ng x g(-1). All soil samples were classified into two categories by cluster analysis. C14-MCCPs and C15-MCCPs, and Cl5-MCCPs and Cl6-MCCPs were the most predominant carbon and chlorine congener groups in most of the samples, accounting for 29.8% and 28.9%, and 29.9% and 23.3%, respectively. C14-MCCPs were the most predominant carbon congener groups in some samples, accounting for 68.5%, which was similar to that of CP-52. Atmospheric deposition and soil-air exchange were the major sources of MCCPs for soils in Chongming. Soils at a few sites were probably contaminated by sewage sludge from sewage treatment plants (STPs) or other unidentified source. No significant correlations were observed between MCCPs and TOC. The correlation analysis also showed significant correlation among the carbon congener groups of MCCPs, which suggested that MCCP congener groups might have been derived from similar sources. Compared to other studies at home and abraod, the MCCPs concentrations in the present study were at a lower level.