Taboo character is typical phenomenon of Chinese characters system, it is considered as the effective key in decrypting the date of Han-Nom texts inscirption texts. Such key is maintained clearly on the ancient books add steles of Vietnam, specially Taboo characters system in the insription texts of Tran Dynasty (1225-1400). Based on research results, we have found a new form of Taboo character previously published in studies in Vietnam Taboo characters. Such new characters forms have helped us easily discover in cription texts at the date of Tran dynasty in Ninh Binh. This is the useful and reliable source for researching of Vietnam Taboo characters in particular and ancient books of Vietnam in general.