Abstract: The generation of fluorescence，the mechanism of fluorescence lifetime and the basic measuring principle for fluorescence lifetime are introduced. A test system for fluorescence lifetimes of pesticides is designed by means of the direct record method(the Photon Counting Technique). According to the natures of the samples under test, a corresponding pulsed light source, optical elements, a semiconducting detector, etc. were chosen. All the working parameters such as the pulsed period of the excitation light source were reasonably optimized, a simple modular design was employed, the fluorescence lifetime of carbaryl solution was measured without the interference of the excitation light, and the fluorescence decay curves and the lifetime of 300～400ps (FWHM) were obtained as the concentration of the carbaryl solution is 500μg／L. The results indicate that the system has the virtues of the simplicity in structure and convenience to operate, and can measure lifetimes as short as the order of 100ps.It is suitable for the quantitative measurement fluorescence lifetime of pesticides which can emit fluorescence.