The invention discloses water-based silk screen ink and a preparation method thereof. The water-based silk screen ink comprises 70 to 75 percent of water-based polyurethane latex, 15 to 20 percent of pigment, 0.8 to 1.5 percent of antifoaming agent, 1.0 to 1.5 percent of dispersant, 0.5 to 1.0 percent of wetting agent, and 1.0 percent of thickening agent. The antifoaming agent is a mixture of polysiloxane or non-silicone amide and hydrocarbon, the dispersant is polyacrylic acid ammonium salt or polyacrylic acid sodium salt, the wetting agent is nonionic surfactant, the thickening agent is alkali-swelling acrylic ester copolymer, and the pigment is pearlied gold or silver paste. The preparation method comprises the following steps: A, firstly filtering the water-based polyurethane latex; B, adding the pigment, the antifoaming agent, the dispersant, the wetting agent and the thickening agent into the filtered water-based polyurethane latex; and C, fully stirring the mixture to obtain the ink. The water-based silk screen ink has the advantages of high temperature resistance, high adhesive strength and high card peeling strength, and is particularly suitable for printing card products.