This experiment was carried out at Agricultural Research Station of Gorgan during summer 2006 to study the effects of corn and green gram intercropping on forage yield, and weed biomass. The experimental design was RCBD with twelve treatments and four replications. A local green gram and corn single cross 550 were the crops employed. The experimental treatments consisted of sole corn and sole green gram along with a series of alternative and additive intercropping systems of the two crops. The results revealed that differences among all treatments for fresh and dry weight of forage per hectare, leaf dry weight of plant unit, leaf dry weight/ plant unit weight, LER and weeds biomass per hectare were significant (? = 0.01). The most fresh and dry weight of forage (50.08 and 15.4 tons per hectare) was obtained from sole corn accompanied with weed control. Maximum leaf dry weight of plant unit (44.13 gr) and LER (1.51) was obtained from corn + 50% green gram treatment. Maximum leaf dry weight/ plant unit weight (43.54 percent) and weed biomass (1109 Kg per hectare) was obtained from sole green gram treatment of no weed control. Minimum fresh and dry weight of forage (11.19 and 3.37 tons per hectare) and leaf dry weight of plant unit (22.04 gr) belonged to sole green gram with no weed control. The lowest leaf dry weight / plant unit weight (16.43 gr) was obtained from no weed control sole corn. Minimum weed biomass (125.3 Kg per hectare) among all the no weeding operation treatments belonged to corn + 50% green gram in the additive intercropping system.