The People's Liberation Army's (PLA) successful test of flight J-20 has surprisd the world. This study planned to investigate PLA's intention and motivations through the ambition of wining the high tech war from the aspects of air force military thinking and the transformation of military strategy. This study is also focused on understanding PLA J-20's capabilities and its impacts to ROC's Joint air defense, and developing counter-measurements for such threat. It is believed that to condcting the prevention measures before such threat is vital for ROC Joint air defense.