The invention relates a three-variable-collar knitwear with neckline made from triangular shell fabric, belonging to the technical field of clothing. The knitwear comprises a fore sheet and a rear sheet, wherein the fore sheet and the rear sheet are formed by folding a rectangular shell fabric; the right central of the folding is provided with a transverse T-shaped neckline (8), and the right and left sides of the folding are concaved with sleeves (9); slots are formed on the edges of the peripheries of the neckline and the sleeves; the fore sheet below the sleeves are sutured with the left and right sides of the rear sheet; the portion of the neckline (8) of the fore sheet and the rear sheet of the knitwear is sutured with buttons along the length direction of the knitwear, namely the vertical opening portion of the transverse T-shaped neckline (8); the waist of the fore sheet and the rear sheet is symmetrically provided with a row of punch holes (7) through which a girdling cotton rope (10) passes; and the neckline (8) is attached with triangular shell fabric (11) on which the fore sheet is buckled by buttons, and a rear sheet button is buckled. The invention provides an extremely simple, fashionable and changeful knitwear, which is simple to manufacture, easy to control quality and capable of reducing manufacturing cost of the enterprise.