The present invention relates to a method for preparing TDI (toluene diisocyanate) isocyanurate by using TDI, monohydric alcohol, solvent, antioxidant, catalyst and termination agent as the raw materials. The properties of the isocyanurate are improved by the process comprising the modification by monohydric alcohol and addition of the catalyst and solvent in several stages at an appropriate temperature. By adding the catalyst and solvent in batches at the condition of controlling both NCO % and the viscosity in the preparation process, and adjusting the solid content at each step, the resulting TDI isocyanurate has low content of free TDI, high xylene tolerance, small product color number, and high performance stability, which makes the product obtained by the isocyanurate have good application properties such as the drying, polishing and extinction properties of coating film, and such isocyanurate has good compatibility with other components.