The quantum computation method has been used to investigate the atomic charge and electrostatic interaction of five models: four of which are composed of two mirror-symmetrical long-chain organic molecules (CH3 (CH2)5–R (R=COOH, CH3, OH) and CH3(CH2)4COOH); and one is composed of two parallel CH3 (CH2)5 COOH molecules. Results show that: (1)The charge of the C atoms of the methylenes(–CH2–) in the molecules is different from each other; (2) the atomic charge is mainly determined by the chain-length and the functional group; meanwhile, it may change when the distance between molecules changes or the arrangement of the molecules changes. The atomic charge in the bimolecular models changes more than in the single molecule models; (3)the electrostatic interaction is mainly determined by the tail function groups: the interaction strength is –COOH>–OH>–CH3; while the other atoms have little contribution. Electrostatic interaction will decrease when the atomic charge of the tail functional groups decreases, which is caused by the increased chain-length.