The invention discloses a preparation method of high-strength water-resistant mildewproof glass cement, which comprises the following steps: preparing a silane-terminated polyurethane prepolymer, proportionally mixing with talcum powder, diatomite powder, lithium bentonite, bamboo charcoal granular powder, -200-mesh cerium oxide, an antioxidant, an ultraviolet absorbent, a plasticizer, a thixotropic agent, benzimidazole carbamate and benzyltrimethylammonium chloridem and adding a binding accelerator and a catalyst. The glass cement is formed by mixing the following components in parts by mass: 60-64 parts of silane-terminated polyurethane prepolymer, 7-9 parts of plasticizer, 18-20 parts of talcum powder, 15-25 parts of diatomite powder, 4-8 parts of lithium bentonite, 8-10 parts of bamboo charcoal granular powder, 2-4 parts of -200-mesh cerium oxide powder, 1.2-1.4 parts of antioxidant, 0.8-1.2 parts of ultraviolet absorbent, 0.2-0.4 part of thixotropic agent, 1-2 parts of benzimidazole carbamate, 1-2 parts of benzyltrimethylammonium chloride, 2.5-3.5 parts of binding accelerator and 0.2-0.4 part of catalyst.