The theory of reversible gelation is shown to be applicable to the hydrogen bonding system by analyzing their similarities in statistical viewpoint. The size distribution of hydrogen bonding clusters, the gelation condition and the generalized scaling law can be obtained directly. These results show that such a system can undergo phase transition process. Furthermore, a relationship between Gibbs free energy of forming hydrogen bond and conversions of groups is given. As an example, the chemical shift of OH groups is considered.