Abstract: To obtain high-purity MgR₂ bulks, using magnesium powder and boron powder as starting materials, MgB₂ bulks were successfully prepared by conventional pressureless sintering (PLS) method in the flowing argon atmosphere at the ambient pressure. We have systematically studied the process of synthesis of MgB₂ and focused on discussing the effects of various parameters on impurity of the sample in the reaction including the sintering temperature, the sintering time and the ratio of starting materials and have obtained the optimal conditions. The experimental results show that MgB₂ bulks with single component were fabricated at 750℃ for 3 hours when the ratio of Mg and B is 1:2 ≤ n (Mg):n (B) ≤ 1.2:2, and its T_c is near 39 K.