The determination of absolute configuration for chiral compounds is one of the most important problem in the organic chemisty, especially for chiral drug synthesis. Density functional theory (DFT/B3LYP) method with various basis sets were employed and verified by calculating the optical rotational properties of two tested chiral compounds, and than applied to the calculations of the optical rotational properties of soman to assign the absolute configuration of soman. The absolute configurations of four isomers for soman are P(R),C(S)-soman→P(＋)C(＋), P(R),C(R)-soman→P(＋)C(－), P(S),C(S)-soman→P(－)C(＋) and P(S),C(R)-soman→P(－)C(－).

Key words: calculation of optical rotation, density functional theory, soman, absolute configuration