Abstract: Residues of 14 pesticides of 3 categories,i.e.,the organochloro-compounds,the organophospho-compound and compounds of analogous dalmatian chrysanthemum,were determined by hyphenation of GC and MS with negative chemical ionization (abbreviated as GC-NCI/MS).Sample of fish was smashed and dispersed with Florisil diatomite and neutral aluminum oxide.The semi-pasty mixture obtained was then extracted with ethylacetate by ultrasonic agitation.After concentration by N2-blowing and addition of 2,2′,4,5′,6-pentachlorobiphenyl (PCB-103) solution as internal standard,the solution was used for GC-NCI/MS determination of the 14 pesticides,with SIM mode.Method of calibration curves with matrix matching was adopted in the qualitative and quantitative analysis.Range of linearity found was from 10 to 800 μg·kg-1 for all of the 14 pesticides,and their detection limits (3S/N) were all less than 1.0 μg·kg-1 (with exception of permethrin and deltamethrin).Recovery was tested by addition of 10,50 and 200 μg·kg-1 of pesticide standards to fish samples,giving values of recovery in the range of 66.6%-102.0%,with values of RSD′s (n=6) less than 12%.