Abstract: GC/MS was used for the determination of the concentration of Neopam(N), Aminopyin(A), Phenacetin(P) in blood. We used Diazepam as internal marking method to cap out correcting quantitation. The regress equation: P Y=1423+401077X, r=0.997; A Y=19329+771338X, r=0.995; N Y=10880+92690X, r=0.996, The precision: P CV=6.9%, A CV=5.2%; N CV=1.8%. The recovery: P=77%; A=82%; N=87%. The minimal detecting amount: p=100ng; A=50ng; N=10ng. The method is accurate, rapid and simple. It can provide scientific evidence for The forensic identification and clinical diagnostics.