A Density Functional Theory (DFT) study is used to calculate structural data of tautomers of 2-Amino-6-methyl pyrimidine-4-one (AMPO) in the gas phase and selected solvents (benzene (non-polar solvent), tetrahydrofuran (THF) (polar aprotic solvent) and methanol (protic solvent), Dimethyl sulfoxide (DMSO) (polar aprotic solvent) and water (protic solvent)) by using PC model. All tautomers are optimized at the B3LYP/6-31++G(d,p). The results show that the tautomer AMPO1 is more stable than the other tautomers especially in water. In addition, stability of the tautomers in deferent solvents shows interesting results and variation of dipole moments and NBO charges on atoms in the solvents are studied.