In order to improve transformation efficiency of maize inbred lines and establish genetic transformation system of maize mediated by Agrobacterium tumefaciens, Agrobacterium strains EHA105 were used to inoculate maize embryonic calli of maize inbred lines 7922 and factors influencing genetic transformation system were studied with GUS as reporter gene. The results showed that: (1) with OD600=0.6 of bacterial concentration, the highest GUS transient expression efficiency was 35.3%. (2) with 15 min of infection time, the highest GUS transient expression efficiency was 37.3%. (3) with 3 days of co-cultivation time and 4 days of resting, the highest GUS transient expression efficiency was highest 29.1%. So OD600=0.6 for bacterium concentration, 15 minutes for infection, 3 days for co-cultivation and 4 days for resting were the best transformation conditions. Genetic transformation system of maize mediated by Agrobacterium tumefaciens was established by optimizing factors influencing this system.