The occurrence of pesticides in the water and aquatic products and the harm of it to human health have gained attention to the governments and scientists. Many highly toxic pesticides have been banned the production and use by many countries and organizations, but because of its persistence and bioaccumulation, pesticides still present in all kinds of water body and aquatic products. The rapid economic development leaded to the capacity and dosage of pesticides increase by past 30 years in China. However, it is not very clear that the pesticide residue status in drinking water, source water and aquatic products. Based on reliable analytical methods, the pesticide residue status of the source and supply water in major big cities of China and fish in the Beijing market were studied. And health risk assessment of pesticides has been studied too. Through this study, the following outcomes were obtained. (1) Based on existing methods, we established pre-concentration method of water and aquatic products and optimized the analytical 25 kind of pesticides method using GC/MS for large-scale investigation of pesticide residue status in drinking water and aquatic products. We have established and optimized the HPLC/MS method for the identification and quantification of two plant growth regulators in source waters by using WCX cartridges for pre-concentration of the samples and using the CAPCELL PAK CR 1:4 column containing strong cationic exchange resins and C18 for separation. It solved the enrichment problem of ionic compounds in water and the pollution problem of ion-pair reagent. (2) Based on the established analytical method, the pesticides residues in 109 source and supply water in 33 cities of China were investigated. The results show that 23 pesticides were detected in the source water, except HCB and heptachlor. The highest detection rates were 56.94% and 50.7%, respectively, for acetochlor and fenobucarb. The highest residue concentrations were 3636.3 ng/L and 3296.1 ng/L, respectively, for atrazine and 2, 4 - butyl ester. The water plants treatment processes cann’t removel most pesticide in water. The average pesticides residue concentration in supply water was 0.01-140.05 ng/L, almost below the national standard limits. The pesticide residues in north water were significantly higher than in the south water and the pesticide residue in coastal was most seriously. (3) We have investigated the pesticides residues in four kinds of fish in Beijing market. The detection rates were high for acetochlor, β-HCH, dicofol, p,p'-DDE, methyl parathion and p,p'-DDT. The highest residue concentration of chlorothalonil was 1779.4 μg/kg, followed by deltamethrin (620.3μg/kg), p,p'-DDT (143.3μg/kg) and α-HCH (114.6μg/kg). Some pesticides showed significant bioconcentration in fish, for example chlorothalonil. (4) The health risk assessment about peistcides in water and aquatic products was studied in this paper. The results suggested that atrazine, DDT, parathion and chlorpyrifos were the prefered controlled pesticides in drinking water. The prefered controlled pesticides in aquatic products were deltamethrin, chlorothalonil, DDT, butachlor, HCH and methyl parathion. The health risks of pesticides in drinking water and aquatic products were lower than 10%. The results suggested that the HRs of pesticieds in water and aquatci products were controllable.