Abstract: In order to establish a simple, quick, efficient and stable system for flax (Linum ustitatissimum L.) transformation, flax seed embryos were used as explants, the experiment conditions (pre-incubation time, coculture time, As concentration, silwett concentration and vacuum time) were optimized with in planta. The best combination was determined as: pre-incubation time of 8 h, co-culture time of 72 h, As concentration of 100 μmol/L, silwett concentration of 0.1%, vacuum time of 5min. The minimum lethal dose of glufosinate was found out for herbicide screening on transformed flax plants. PCR identification on surviving plants showed that positive transgenic plants were acquired successfully. The optimization of in planta transformation into flax seed embryos was achieved, and had great value in practical application.