Mutations induced by gamma irradiation are part of improving some important agronomic traits in crops.  Identifying the optimal mutagenic dose is considered to be the most crucial step in trials and generating mutated genetic materials. The goal of this study was to evaluate the effect of different doses of gamma ray (0, 150, 200, 250 and 300 Gy) on some plant early stages traits and biochemical characteristics in SC704. Based on the probit analysis, the optimum gamma irradiation dose for induction of mutation in SC704 were 212.69 Gy. Significant differences were observed for irradiation dosage in all growth traits, including root length, shoot length, root fresh weight,  shoot fresh weight, root dry weight and shoot dry weight, plant height and survival percentage. As the dose level increased, total carbohydrates, malondialdehyde, hydrogen peroxide and catalase and peroxidase enzymes increased.