Abstract: The quantum chemistry CNDO/2 method introduced with external electric field perturbation is used to calculate the energies and the electronic polarizability of polyacene homologue (C_4n+2,H_2n+4).The results indicate that the polarizabilities of total and л electrons in crease with the increasing of the ring numbers, but the increasing rate reduces gradually.When n is large enough, the increasing rate tends to be a constant.The increasing rate of polarizability along the direction of molecular chain is much larger than that along other directions.The increasing rate of л electronic polarizability is generally higher than that of the total one.The stability laws of polyacene homologue are: the stability of the trans-type is about the same as that of the cis-type.Both of them are more stable that the average-bond type.The energies of all systems.decrease when the length of molecular chains are gradually increased.The decreasing values reduce a little with the increasing of the length of molecular chains.

Key words: Polyacene, Electronic polarizability, External electric field perturbation