An application of derivative technique in the signal processing of gas chromatography(GC) is described. TCD's sensitivity of the derivative GC was 270 kV.L/kg, and its susceptibility was 0.3 microgram/L In comparison with the conventional GC, there was a 7-40 fold increase in sensitivity and a 24-40 fold decrease in susceptibility. The noise of the derivative GC was equal to or smaller than the conventional one. The minimum resolution for a pair of substances most difficulty to be separated in conventional GC, which was separated completely in the derivative GC, was 2.8. The linear range of n-butanol was 10(2) and the peak area correlation coefficient of the derivative GC was 0.9991.