The invention provides a preparation method of nanocluster composite substrate AuNPs@ (SG) X used for detecting Pb<2+> by aggregation-induced emission, and belongs to the technical field of analysis and detection. The method includes the steps of (1) mixing HAuCl4 aqueous solution with GSH solution, adding ultrapure water to the mixed solution, and stirring the mixed solution at a certain temperature to form floc precipitation; (2) adjusting the pH value of the mixed solution to 5-6, making the precipitation completely dissolved and the mixed solution clear and transparent; (3) after aging the mixed solution for 1.5-3 h, adjusting the pH value of the mixed solution to 7.2-8.5 to obtain the nanocluster composite substrate AuNPs@ (SG) X. The preparation method adopts the direct reaction of HAuCl4 and GSH to prepare the AuNPs@ (SG) X in one step, and the synthesis method is simple and controllable. The nano Au-ion of the nanocluster composite substrate AuNPs@ (SG) prepared by the method is well dispersed to almost not overlap and aggregate, and the synthetized composite substrate mixed solution presents colorless, clear, transparent and stable under the visible light; moreover, the composite substrate prepared by the method has the advantages of strong selectivity and no self-fluorescence, and is favorable for further inducing metal ions to produce aggregation emission, and studying high sensitivity sensing.