MC-LR possessing strong hepatotoxicity, potential carcinogenicity, and biological toxicity could have an intensive influence on human health and the aquatic ecological environment and need to be monitored critically. For the specific and highly sensitive analysis performance, agold-magnetic composite nanoparticlemodified by aptamer-cDNAfluorescent hybridization probe (Fe3O4@MIL-101-NH2@Au@aptamer) was prepared and applied for sensing detection of MC-LR in water with laser-induced fluorescence (LIF). This work studied the feasibility, optimization of analysis conditions, specificity, stability of the method, and sample analysis application. As a result, a high Brunauer-Emmett-Teller (BET）specific surface area of 114.02 m2·g-1 was achieved in Fe3O4@MIL-101-NH2@AuNPs, which resulted in a high modification rate of up to 98.8% achieved for aptamer-cDNA fluorescenthybridization probe. With the excitation wavelength of 497 nm, the aptamer-cDNA fluorescent probe has a strong fluorescence response with the emission wavelength of 512 nm to the trace MC-LR. Under the optimal conditions (pH 7.5, NaCl concentration 500 mmol·L-1, nanogold size 20 nm, analytical time 30 min), a good linear relationship between MC-LR concentration and fluorescence intensity was achieved in a wide linear range (0.020~3.000 μg·L-1) with the limit of detection (LOD) as low as 0.006 μg·L-1, which was 1.6~22.3 folds better than that of the most fluorescence methods reported previously. The relative standard deviation (RSD) of intra-day, intra-day, and inter-batch was gained in 1.7%~8.8%, and the relative error (RE) of -4.3%~4.1%. High specific selectivity and low cross-reactivity for MC-LR (1.0 μg·L-1) were also achieved using theas-prepared fluorescent probe, even if the concentration of interfering toxins (MC-RR, MC-YR, OA) was 100 folds higher than that of MC-LR. The fluorescence responses of MC-LR in these mixtures werewell consistent with that of MC-LR in the standard solution. Applied to the analysis of samples from the Minjiang River, Lake Water, and the inland river, the identification of MC-LR in water samples was satisfactory. The recovery yields of MC-LR for three concentrations (0.050, 0.100 and 1.000 μg·L-1) rangedin (90.1%±6.4%)~(104.2%±7.0%) (n=3). The results were consistent with those obtained by the LC-MS method ［（91.3%±7.0%)~(104.4%±2.0%), n=3］. It might light a new technique for the specific and rapid monitoring technology for tracing MC-LR in the environmental water.