The utility model relates to a one-step stereo smocking forming seamless coat which comprises knitted collar, coat body and sleeves, wherein the collar and sleeves are connected with the coat body by sewing respectively. The one-step stereo smocking molding seamless coat is characterized in that the collar body adopts rib stitch, and the neckline adopts weft plain stitch; the coat body is woven and formed at one step; stereo creases are arranged at the chest part; the part from the abdomen to the lower hem adopts rib stitch, and the rest adopts weft plain stitch; the part of each sleeve, close to the cuff, adopts rib stitch, and the rest adopts weft plain stitch; and the neckline and the cuff have double-layer edges and adopt weft plain stitch. The coat provided by the utility model is comfortable and beautiful to wear, has good elasticity and shows the female figure curve; and the processing flow is simple and the production cost is reduced.