This paper makes systematic interpretation on the theory of“tranquillization for strengthening vital qi”,from the relationship between insomnia and deficiency syndrome and the therapeutic effects of tranquillization in internal damage,miscellaneous disease and deficiency syndrome. Sleep is an important way to restore vital qi. Deficient diseases and syndromes are often accompanied with insomnia,which caused by insufficiency of qi and blood,malnutrition of zang-fu organs,yang failing to enter yin. Deficiency syndrome also can be aggravated by insomnia,even presents the tendency of “deficiency,loss and overexertion”,which lead to the poor prognosis. Therefore,the theory of“tranquillization for strengthening vital qi” is proposed. It is considered that tranquillization can be used in the treatment of deficient diseases as adjuvant therapy,which regulates sleep and induces yang into yin in order to restore vital qi.