ABSTRACT In this paper, silica‐strontium aluminate (SrAl 2 O 4 : Eu 2+ , Dy 3+ ) hereafter referred to as SiO 2 SrAl 2 O 4 : Eu 2+ , Dy 3+ were prepared by the solution gel method using tetraethoxysilane (TEOS) as the silica source. An SiO 2 protective layer was formed on the surface of the strontium aluminate phosphor after drying, which provided the strontium aluminate phosphor with a high degree of water resistance. The pH of its aqueous solution remained at 8.5 after being placed in water for 400 min, after which the fluorescent wood‐plastic composite 3D printing substrate was prepared. This was achieved by utilizing Poly Lactic Acid (PLA) and poplar wood flour as the substrate, with the addition of the SiO 2 SrAl 2 O 4 : Eu 2+ , Dy 3+ phosphor. The preparation of the fluorescent wood‐plastic composite (WPC) 3D printing substrate is outlined below. The composite 3D printing substrate has been found to demonstrate a tensile strength of 48.64 MPa when subjected to an SiO 2 Al 2 O 4 : Eu 2+ , Dy 3+ phosphor content of 4%; at the same time, it has a good fluorescent effect. The substrate has been shown to enhance the versatility of PLA composites and reduce the cost of fluorescent WPC. These materials are both waterproof, making them suitable for a wider range of applications. They exhibit favorable nighttime fluorescent properties and permit experimentation with personalized customization through 3D printing.