Abstract: Taking the commercial mixed yogurt as research object, the fluorescence spectra of yogurt samples with different numbers of lactic acid bacteria were obtained by the self-developed laser induced fluorescence（LIF） system. The correlation between the peak of various fluorophore produced by lactic acid bacteria in yogurt and the number of lactic acid bacteria was discussed.The quantitative prediction model of the number of lactic acid bacteria in yogurt was established. The results show that the fluorescence peaks at about 435, 485 and 520 nm can be identified, and the fluorescence peaks show regular changes with the variation of lactic acid bacteria. The original fluorescence spectrum of yogurt was corrected by four types of light scattering correction methods, and the lights cattering correction algorithm of OPLEC+SR can effectively eliminate the effect of baseline drift related to the wavelength with the optimal PLSR prediction model results. The correlation coefficients of correction set R_c and validation set R_p are respective 0.965 4 and 0.953 3, and the root mean square errors of C_RMSE and P_RMSE are respective 0.152 5 logCFU/mL and 0.236 2 logCFU/mL. According to the validation result of the proposed method with the independent set of 8 samples,the correlation coefficient R after linear fitting of the measured and predicted values can reach 0.951 0 with the residual modulus of 0.860 6, which demonstrates that the proposed LIF system can meet the requirements of real-time monitoring of the number of lactic acid bacteria in yogurt.