The theoretical calculations methods DFT/STO-3G, DFT/6-31G, DFT/6-31G(d,p), HF/STO-3G, HF/6-31G and HF/6-31G(d,p) are used to determination the physic-chemical parameters for some aliphatic amine. This data was used to predict pKa values. Two methods of statistics are used to evaluate the pKa depends on the theoretical data. The first statistical method is used G data to determine the pKa. The second statistical method depends on the enter all the thermodynamic and physic-chemical values in the equation using multiple linear regression. Finally, the two methods are compared with experimental.