The T91 was designed to counter the People's Liberation Army's deployment of Type 81 assault rifle and the QBZ-95.

[1] There are rumors that arms dealers had secretly inquired about the possibility of sales to certain militant groups in Southeast Asia, but were reportedly rejected by the Republic of China Ministry of National Defense (MND).

[citation needed] In 2005, the Taiwanese Military Police ordered 12,069 T91 combat rifles to equip garrison units in the Taipei capital region.

[4] The T91 is a gas-operated short-stroke, air-cooled, rotating bolt, magazine- or drum-fed, select-fire, modularized military rifle compatible with various tactical accessories.

Similar to the T86, the T91 is shorter than the T65K2 assault rifle, giving the operator higher mobility and ease of aiming in a confined space.

The T91 also inherits the modularized gas piston system from the T86, allowing easy removal for maintenance without the risk of losing small parts.

The telescoping stock on the T91 was designed based on the experience of military and police personnel with the M4 Carbine.

Standard-issue 30-round detachable box magazines for the T91 feature indicator holes for the top 2-15 rounds as well as two protrusions on each side to avoid over-insertion.

The Chung-Shan Institute of Science and Technology developed a T91 indoor shooting simulator for infantry marksmanship training.