The invention relates to a preparation method of a nylon-6-based polyesteramide fiber. The method comprises the steps of carrying out melt spinning on a nylon-6-based polyesteramide polymer to obtainthe nylon-6-based polyesteramide fiber. A preparation method of the nylon-6-based polyesteramide polymer comprises the steps of mixing nylon-6 prepolymer ester with a polyester prepolymer and then carrying out an ester exchange reaction to obtain the nylon-6-based polyesteramide polymer. The nylon-6 prepolymer ester is prepared by firstly synthesizing a dibasic-acid-terminated nylon-6 prepolymer and then adding dihydric alcohol to enable dihydric alcohol to react with carboxyl of terminal groups. According to the preparation method of the nylon-6-based polyesteramide fiber, the nylon-6-based polyesteramide polymer is obtained through a copolymerization approach, so that the uniformity of nylon-6 and polyester blocks is improved, and the phase domain is controllable; polyesteramide slices containing polyester chain segments at different ratios can be obtained by changing the addition quantity of the polyester prepolymer, so that the sequence structure is controllable, and the polymerization process is flexible. The prepared fiber has high spinnability and stiffness and can be applied to the fields of clothing, home textiles, automobile interior decoration and the like.