Abstract: Ten samples of human urine were collected from various multitudes, and a series of the urine samples were prepared by addition of mixed standard solutions of the 3 drugs, meperidine, methadone and cocaine to the 10 urine samples with their concentrations of 1 and 2 fold of the detection limits and 1, 1.5, 2, 4, 6, and 8 fold of the lower limits of determination. Each of these samples was pretreated as follows:1.0 mL of the urine sample was taken and added with 15 μL of 100 g·L^-1 NaOH solution and 20 μL of the internal standard solution of 100 mg·L^-1. Then the solution was ultrasonically extracted with 1.0 mL of cyclohexane. After centrifugation, an aliquot of 200 μL of the supernatant was taken for GC-MS determination according to the working conditions of the instruments. Standard curves were prepared by addition of standard stock solution of the 3 drugs to blank urine samples and treated as described above. Detection limits (3S/N) of 0.10, 0.30, 0.15 mg·L^-1 were found for the 3 drugs respectively. About more than 6 000 data obtained in the analysis were treated statistically by using Spss software. The absolute deviations of retention time of the 3 drugs were found within ±0.04 min (2.4 s), and relative deviations of relative retention time of the 3 drugs were found to be within ±0.1%. Determination ranges of absolute deviations and relative deviations of ionic ratios of characteristic ions were ±20% and ±50%, respectively. The results obtained were the practical data and theoratical basis for judgement of analytical results of the 3 common drugs in urine.