Deqi is the key for therapeutic effect of acupuncture therapy. In the present paper, the significance of Deqi, and how to differentiate qi and how to induce Deqi are preliminarily studied. Deqi is concrete response of acupuncturist and the patient during acupuncture. Arrival of qi is like bobbing on water when the fish swallows the fishhook; no arrival of qi is like the deep valley with shallow sensation. For differentiation of qi, the vital-qi (essence derived from food), pathogenic factor, deficiency and excess, cold and heat need to be differentiated. For manipulation, the 14 methods of Yang Ji-zhou are used as guiding principle. In brief, massage along channel induces qi, on-the-point pressing promotes flow of qi, circling method regulates qi. And reinforcing and reducing by puncturing along and against the direction of channels respectively are explained, and how to induce Deqi is preliminarily expounded from methods of inserting the needle, manipulating the needle and withdrawing the needle.