This paper describes another use of borane containing polyolefins, which are served as intermediates for the preparations of polyolefin graft copolymers, such as PP-g-PMMA, PP-g-PVA, polyoctene-g-PMMA, EP-g-PMMA, Butyl Rubber-g-PMMA. In general the copolymer has polyolefin backbone and several free radical polymerized polymers bonded at the side chains. The chemistry to prepare this type of graft copolymers is based on the graft from reaction by using the borane containing polyolefins. It is interesting to note that one of the additional advantages in borane initiators is the ability to initiate the polymerization at low temperature. Peroxides and azo initiators when used alone usually require considerable heat input to decompose and thereby to generate free radical. Elevation of the temperature often causes significant reduction in molecular weight of polymer accompanied by the loss of important properties of the polymer.