Abstract: By using bulbous tubers of ‘Pollyanna’ as the gene transformation acceptors, the ACO gene was transferred into lily with Agrobacterium tumefaciens-mediated transformation. The factors which affected transformation were studied. The results suggested that the minimum contamination rate was gotten when the bulbous tubers were used as acceptors. It was better for Agrobacterium tumefaciens instrusion with OD600=0.8 in 30 min. Agrobacterium tumefaciens which was activated for 1-2 h tended to differentiate resistant plants. The differentiation rate of resistant plants could be increased by adding into 20 mg/L AS in MS liquid and solid co-cultivation medium. NH4NO3-free medium could improve the transformation rate. PCR screening showed that some Kanamycin resistant plants were positive, which indicated preliminarily that the ACO gene had integrated into Lily’s genome.