This invention provides one-pot reaction for digesting polycarbonate waste with alkylene glycol in the presence of a basic catalyst at 180° C. under normal atmospheric pressure. The digested product mixture was found to consist of bisphenol A (BPA) and monoalkoxylated and bisalkoxylated diols of BPA. Alkoxylation of BPA and monoalkoxylated diols of BPA is performed by adding urea or urea derivative (or carbonic acid ester or amine ester) to the digested product mixture at a high temperature under normal atmospheric pressure to obtain the final product, i.e., bisalkoxylated diols of BPA in high yield. The bisalkoxylated diols of BPA may be used as raw materials to synthesize polymer such as polyurethane (PU) or polyester.