There is a growing demand for bio-based and biodegradable polymers as a solution to problems concerning energy resources, global environment and solid waste management. Researches on such polymers have been carried out for achieving a balance between human activities and natural environments. Ideal biodegradable polymers are produced from renewable resources and degraded completely to carbon dioxide & water by the action of microorganisms. From these considerations, Polyhydroxyalkanoates PHA appear to meet these criteria; however, it has some unfavorable properties. The modification of PHA is a promising method for the preparation of new materials which enables one to induce special properties such as biodegradation, swelling and antimicrobial activity and enlarges the field of the potential applications of these biopolymers. Among the diverse modifications, grafting with polymers is a convenient method. In this work, grafting of PHA with some selected monomers was investigated. The effect of reaction variables as initiator, monomer concentration and reaction time on the grafting parameters such as grafting yield and grafting efficiency have been studied systematically.