This disclosure relates to a method for preparing a catalyst for synthesis of a polyolefin and a process for synthesis of a polyolefin using the same. More particularly, this disclosure relates to a method for preparing a catalyst for synthesis of a polyolefin including: reacting a magnesium compound with an alkane diol having a carbon number of 3 to 15 unsubstituted or substituted with an alkyl group having a carbon number of 1 to 5, and a benzoyl halide compound to prepare a magnesium compound solution; reacting the magnesium compound solution with a first transition metal compound to prepare a support; and reacting the support with a second transition metal compound to produce a solid catalyst, and a process for synthesis of a polyolefin using the same.