Male adult forked-tailed sunbird (named subspecies) is green from the top of the head to the back of the neck, with metallic luster, black down on the back, bright yellow waist, dark brown wings, olive yellow on the outer edge, metallic green on the upper tail and central tail feather, or blue-purple under different refraction, with the apex of the central tail feather shaft extending like a needle, and four pairs of tail feathers on the outer side having clear white terminal spots and emerald green feathers. The eyes, cheeks and ears are all black, the head side is brownish red, the mustache green is metallic or purplish red, the chin, throat and upper chest are dark brownish red, the lower chest is olive yellow, sometimes mixed with grayish brown, the lower body is light green yellow, but not bright, the lower chest is gray, the lateral abdomen is silky white or yellowish, and the wings are covered with white feathers.

The base of the female adult bird's crown or feather is grayish brown, the upper body is olive yellow dyed green, the wings are dark brown, the narrow side is olive yellow, the tail feather is brown black, the central tail feather axis is not prolonged, and the lateral tail feather has obvious white feather ends, which gradually become larger outward; The eyes are gray-black, the head is light olive green, the chin and throat are gray-green, the chest is dark gray-green, the abdomen is gray-green, and it gradually fades, and the feathers under the tail are light milky yellow or milky white.

The feather base of the young bird's crown is light dark brown, the head and neck are gray-green, and the lower body feathers are velvet; Laryngeal gray is slightly yellowish green, chest is yellowish green, abdomen and sides are yellowish, and the rest are similar to female adults.

South China subspecies and named subspecies are similar in special tail shape and feather color; The adult male bird of South China subspecies has olive green back and red throat and chest. The upper olive body of female adult birds is yellow-green, which is brighter than that of the named subspecies. The lower body coat color of the two subspecies is unstable, and the variation of coat color has nothing to do with season and distribution height.

Fork-tailed sunbirds are slender; The mouth is slender and bent downward, and the apex of the upper and lower mouth edges is about 1/3 in a fine sawtooth shape; The wings are short and round, the first primary flight feather is short, and the tail is wedge-shaped; Tarsometatarsal is slender and has peltate scales. Adult male bird weighs 5.0 ~ 7.0g, with a total length of 9.5 ~1.5cm, wings of 2.5 ~ 3.0cm and tail of 4.0 ~ 5.2cm; female bird weighs 4.5 ~ 7.0g, with a total length of 7.9 ~ 10.0cm and wings of 4.2 ~. ..