This paper describes the clinical experience on treating severe insomnia by applying classical prescription. The author pointed out that the key of applying classical prescription was paying attention to the classic texts，prescription-syndrome differentiation, using the original prescription and the original amount. The Egg yolk was indispensable when Huang-lian-e-jiao formula was used for treatment of insomnia. Suan-zao-ren needed to in large dosage when Suan-zao-ren formula was used for treatment of insomnia.