A printing ink for a washing-free cold transfer printing process and a method for printing a polyester fabric by using the printing ink are provided. The printing ink includes a thickener, a disperse dye, a binder, a surfactant, a dispersant and water. The thickener is a waterborne polyurethane thickener with a solid content of about 20-40% and preferably about 25-35%, and the waterborne polyurethane thickener has the following structure:

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where m is 8-20, preferably 8-15, n is 15-25, preferably 17-20, and k is 1-8, preferably 2-6.