The additional Paveway IV bombs – manufactured by Raytheon – will be carried by Tornado jets in Afghanistan, and are also due to be carried by new Typhoon and Lightning II aircraft.
Used during last year's air campaign over Libya, the precision weapons use GPS technology to enable 24-hour attacks against a wide range of targets.
The contract will sustain about 450 jobs at the firm's UK plants – 300 in Glenrothes, Scotland, responsible for the guidance control section of the weapon, and 150 in Essex.
The contract will also support jobs at Raytheon's subcontractors – Chemring in Ardeer, Ayrshire, Portsmouth Aviation Ltd, Exelis in Brighton and Thales in Hampshire.
This year, the MoD has awarded more than £100m of contracts to Raytheon UK for 1600 Paveway IV bombs, a spokesman said.
Minister for Defence Equipment, Support and Technology Philip Dunne said: "This sophisticated UK-developed and manufactured weapon is the backbone of the RAF's precision bombing capability.
"This contract will maintain hundreds of skilled jobs."