Recently, optical polymer lenses are being used in many digital modules, especially for mobile phones and smartphones. And high refractive index polymers containing 9,9-Bis [4-(2-hydroxyethoxy) phenyl] fluorene (BPEF) and Bisphenol-A (BPA) polycarbonate resins had been developed for those lenses. As those lenses were precision-machined to close tolerances, higher flux were required. To realize higher flux, lower molecular weight polymers were used. But few literatures about optical and thermal properties of low polymerization number (Pn) polymers had been reported. We have already reported that the influences of average Pn and terminal group on a refractive index (nd) and a glass transition temperature (Tg) of BPEF polycarbonate. And in this study, the influences of average Pn and terminal group on a refractive index (nd) and a glass transition temperature (Tg) of BPA polycarbonate were investigated. Various Pn of BPA polycarbonate were synthesized by transesterification method. Pn and terminal end group, which are hydroxyl terminated and phenolic terminated, were easily controlled by this method. In the case of hydroxyl terminated BPA polycarbonate, nd decreased with increasing Pn. And, in the case of phenolic terminated BPA polycarbonate, nd also decreased with increasing Pn, and both converged to same value in high Pn region. And we also found that the both of hydroxyl terminated and phenolic terminated BPA polycarbonate converged to same value in high Pn region. They were in the same trend.