The invention discloses a preparation method of a fluorescent composite material based on MOFs/porphyrin. The method comprises the following steps: dissolving zinc nitrate, terephthalic acid, N-polyvinylpyrrolidone and lauric acid into N-N dimethylacetamide, and performing hydrothermal reaction, cooling, centrifugation, ethanol washing and vacuum drying, so as to obtain an H-MOF-5 nanosheet; dissolving the H-MOF-5 nanosheet into an ethanol solution, and performing ultrasonic mixing, so as to obtain a mixed solution; stirring, adding porphyrin into the mixed solution, ensuring that the porphyrin is completely dissolved, and continuously stirring at a room temperature, so as to obtain a mixture; performing centrifugation on the mixture, separating out a product, and performing ethanol washing and centrifugation and vacuum drying, so as to obtain an H-MOF-5/TCPP fluorescent composite material. The method has the advantages that porphyrin molecule is loaded to the H-MOF-5 nanosheet, the aggregation of the porphyrin molecule is prevented, the water solubility and fluorescence property of the porphyrin molecule is improved, and the morphology consistency of the material before and aftercompounding is kept, so that the fluorescent composite material has an important effect in terms of fluorescence sensors.