Abstract: The determination ofβ-phenyllactic acid( PLA)in rat plasma by derivatization capillary gas chromatography is described. Quantitation was affected by ⁶³Ni-electron capture detector after separation with a SE-54 quartz capillary chromatographic column. Calibration curves were linear within the range of 1.6～9.6μg·ml^-1.The limit of detection of PLA was considered to be 0.5 μg.·ml^-1. PLA was extracted from plasma with ethyl acetate(rat plasma 0.1ml).The recovery from plasma was high and the mean value was 98.11±3.81(s)%,their within day and between day relative standard deviations were 5.13%and 5.9%respectively.