The invention discloses baking varnish for a ceramic tile surface and a preparation method of the baking varnish. Low-carboxyl acrylic resin and synthetic fatty acid resin are taken as main film forming materials and cooperate with an isocyanate trimer which is used for auxiliary curing, so that chemical reaction between the baking varnish and white water-based paint can be avoided. A construction process of the baking varnish is simple, the technical requirement is low, an unskilled worker can also perform construction operation, and the labor cost is saved.