Brown and white on the male head of red-spotted duck; Cheeks, throat, front neck and neck side are light brown; There is a narrow black collar at the base of the lower part of the neck during the breeding season; The chest, upper back and shoulders are reddish brown; The back waist is slightly lighter; The waist feathers are brown with dark brown moth-like spots; The tail and tail are covered with black feathers; The wings are covered with white feathers, slightly brown; The winglet and the first flight feather are dark brown, the second flight feather is bright green, forming a bright green wing mirror, and the outer third flight feather is brown; The lower body is brown, with the deepest feathers on the upper chest, lower abdomen and lower tail; Axillary feathers and alar feathers are white. The female bird's feather color is similar to that of the male bird, but the body color is slightly lighter, the top and side of the head are almost white, and there is no black collar at the root of the neck. Young birds are similar to female birds, but slightly darker and grayish brown, especially on the head and upper body. The iris is dark brown, and the mouth and accessories are black.

Size measurement: weight: male 1000- 1656g, female 969-1689g; Body length: male 5 16-670mm, female 510-680 mm; Mouth peak: male 42-50mm, female 36-46 mm; Wings: male 350-390mm, female 312-380 mm; Tail: male 1 15- 165mm, female115-165mm; Metatarsal bone: 54-63mm for male and 50-58mm for female.