The J-31 is a mid-weight, twin rudder and twin-engine jet with the typical configuration that is commonly shared by other 5th generation fighters such as Sukhoi T-50. J-31 incorporates certain stealth characters such as forward swept intake ramps with diverterless supersonic inlet (DSI) bumps, trapezoidal wings and a two-piece canopy.
The J-31 appears to be a smaller and more agile aircraft than the Chengdu J-20 that resembles a twin engine F-35C. This may be because it might be used as a fifth generation carrier based fighter. Another feature that the J-31 shares with the F-35C (and most other carrier based fighter jets) is the twin forward wheels. Bill Sweetman has cited several improvements to the F-35C design files the Chinese may have acquired in the J-31. Like the F-35, the J-31 has two internal weapons bays that can each carry two medium range missiles, along with two heavy hardpoints and one light hardpoint on each wing, but while it seems to have added an additional light hardpoint to each wing over the capacity of the F-35, it seems to lack the capacity of the F-35 to mount a centerline gunnery or jamming pod.
Vladimir Barkovsky of Russian Aircraft Corporation MiG (formerly known as the Mikoyan-Gurevich Design Bureau) has stated that, despite some design flaws, the J-31 "looks like a good machine." Although it contains features already in use on the U.S. fifth generation fighter designs, it is "not a copy but a well done indigenous design." Barkovsky has confirmed that the engines on the prototype aircraft are RD-93s. However, China already has an engine similar to the RD-93, the Guizhou WS-13 currently installed on the JF-17 which has the same thrust and size of the Russian RD-93. China is working on an improved variant named WS-13A with 100KN of thrust for use on the J-31. Lin Zuoming, chairman of China's AVIC, has said that he hopes to put domestic engines on the fighter.
As the Chinese build up confidence in newer, more reliable and powerful domestic engines, they may be able to power the J-31 sooner than the larger J-20 and in greater numbers.
USAF Lieutenant General Charles Davis has said that while the Chinese fifth generation fighter may have used stolen information from the F-35 program, it was unlikely to measure up to the American aircraft.
Unlike the F-35's "baked in" fiber-mat stealth, the J-31 uses stealth coatings.
The J-31 has a flatter fuselage than the F-35; which suggests a more pronounced air superiority focus for the J-31, since a flatter fuselage results in a smaller weapons bay but improves fuel efficiency and speed by decreasing aerodynamic drag.