All the previous contributions on electron-LO phonon interaction in quantum dot structures are based on macroscopic isotropic models. The macroscopic dielectric model taking account of the phonon confinement points out that the interaction strength between electron-hole pair and LO phonon (eh-ph) in semiconductor quantum dots is size-independent that is not in accord with some of the experiment data. In this article, after taking account of the effect of transverse charges of ions, microscopic valence force field model based on group theory is used to evaluate the eh-ph and exciton-LO phonon (ex-ph) interactions in GaAs QDs with scales up to 90Å (containing 16863 ions). It turns out that both the interaction strength of eh-ph and ex-ph are not size-independent but size-sensitive.