Formations of thio-thiol and keto-enol tautomers of ۲-thiouracil (۲TU) were investigated in this work for performing structural analysis by means of density functional theory (DFT) calculations. To this aim, existence of all possible structures were examined by movement of hydrogen atoms of amine groups to each of original thio and keto groups for formation of thiol and enol groups for new structures. Optimization calculations were performed to reach the minimum energy level for each investigated structure. The results showed that occurrence of such tautomerism processes could yield new features for the corresponding structures, in which variations were more or less significant in comparison with the original features. The important note is that formations of tautomers were possible meaning changes of expected activities regarding occurrence of such process in order to the concept of structure-activity relationship. Therefore, such computer-based works could provide information for examining such features in the tautomers of ۲TU, as a compound related to pharmaceutical applications, to manage somehow the structural features for the specified purposes.