A new rapid detecting method (called dynamic measurements) was reported to detect and distinguish the presence of two pesticide gases and their mixture in the ambient atmosphere. The method employed only a single SnO2-based gas sensor in a rectangular temperature mode to perform the qualitative analysis of pure pesticide gas and a binary gas mixture (acephate and trichlorphon) in air. Experimental results showed that a high selectivity of the sensor was achieved in the range of 250–300°C and modulating frequency 20mHz. The quantitative analysis between the pure pesticide gas and the mixture was performed by a fast Fourier transformation (FFT). The higher harmonics of the FFT characterized the nonlinear properties of the response at the sensor surface. The amplitudes of the higher harmonics exhibited characteristic changes which depended on the gas concentration and the kinetics of the gas species on the sensor surface.