The Agrobacterium tumefaciens mediated genetic transformation system of soybean embryonic tips was optimized. The experiment was carried out by orthogonal test involving four levels of five terms (Acetosyringone (AS) concentration, Agrobacterium OD value, infection time, co-culture time and recovery culture time) , and the transgenic events were ascertained by β-glucuronidase assay. The results indicated that the optimum transformation conditions were: 100 μmol/L AS, Agrobacterium OD of 0.9, infected for 15h, co-cultured for 5d, recovery cultured for 3d. In the above condition, GUS staining positive rate reached up to 74.59%. And then, transgenic plants were obtained by PCR and RT-PCR. Using the optimized system, a stress-resistant gene GmPK was transformed. PCR and PCR-Southern blotting results showed that the GmPK gene was integrated into the genome of soybean. The transformation efficiency was 0.6%.