In order to realize on-line measurement for pesticide residua in soil,a fiber-optic fluorescent measuring system was put forward.The foundational principle of organic molecules emitting fluorescence and the feasibility of measuring pesticides by fluorescence method were analyzed.Then,a fiber-optic fluorescent measuring system was established based on the techniques of fiber-optic sensing and fluorescence analysis.In the system,a pulsed xenon lamp was used as an excitation lamp source and a self-made cone-shape fiber-optic probe was used for detecting the fluorescence,a small-sized flat field grating spectrometer for dispersing fluorescence and a high-speed datum-collecting module for collecting and converting the fluorescent signals.The fluorescence spectrum of the pesticide could be obtained with only one exposure of the system.In this way,the fluorescence experiments on carbaryl of different concentrations in soil were carried out and the working curve and the minimum detecting limit of the system were examined.Experimental results show the system can get high-resolution fluorescence spectra with a linear relationship between the fluorescence intensity and the concentration in the range of 0.005～0.1 mg/kg.For the Limits of Detection(LOD) of 0.005 mg/kg and the Relative Standard Deviation(RSD) of ≤3 %,the system can surely meet the needs of detecting pesticides in soil.