The T-70 was designed by, N. A. Astrov, who wanted to create a light tank that had more armor, a larger gun, and better cross country capabilities than the T-60.
Though the T-70 was a decent design, many felt it wasn't an improvement over the T-60.
The turret was place on the left side. Two engines were mounted in tandem on the right side. Each engine drove a track. The differential and main clutch were united with the engines in one block. The T-70's idler was in the rear and the power in the front.
In September 1942, strengthened running gear was installed. The tracks were widened to 300 mm, and the road wheels and return rollers were made wider. The drive wheels and drive shafts were improved.
The 45 mm gun fired a 3.2 lb APHE shell at a muzzle velocity of 2,500'/sec.
The turret could only hold one man, the commander who also was the loader and gunner for the 45 mm gun. There were some attempts to install an automatic loader for the 45 mm but these were unsuccessful.
The driver had an armored visor installed.
Crews didn't like the tank as its fuel tanks were easy to ignite.
Starting in September 1943 the T-70s started to receive the GAZ-203 engine (85 HP).