Phthalates (PAEs) are esters of phthalic acid, which is one kind of environmental estrogens. They are potentially toxic to human health due to their endocrine-disruptive effects. PAEs are not chemically bound to plastics and can therefore be easily released into the environment. Consequently, these compounds are ubiquitous in environmental matrices. The danger of phthalates to humans and animals has become a major health concern. More and more researchers are working at developing methods to determine phthalates. Nowadays, the most widely used method is chemical analysis method, which is carried out by chromatographic instrument including GC, GC-MS, HPLC and HPLC-MS. In this paper, we developed two kinds of sample pretreatment methods: dispersive solid phase extraction and GPC-LC-MS online clean up and concentration system, which are used to detect PAEs coupling with LC-MS. The dissertation consists of the following three chapters. Chapter 1 The toxicity, danger and distribution of phthalates are introduced in this chapter. Besides, the detection methods of phthalates are presented. Chapter 2 In this study, a simple, rapid and sensitive method for the determination of five phthalates in fruit jellies by LC coupled with MS has been developed. Acceptable accuracy and precision were obtained. Chapter 3 An online clean up and concentration system were developed to determine PAEs. This online system consists of three parts: GPC clean up part, ODS concentration part and LC-MS detect part. All conditions were optimized and the results were discussed. Key words: Sample pretreatment method, Phthalates, Dispersive Solid Phase Extraction, GPC-LC-MS Online System