Blends of a high density polyethylene (HDPE) matrix and a polycarbonate (PC) minor phase were investigated through their morphology, heat resistance, mechanical properties, crystallizing behavior, rheological measurement and especially the compatible effect of a compatibilizer : low density polyethylene grafted diallyl bisphenol A ether (LDPE-g-DBAE). The blends without compatibilizer exhibited a phase growth and no adhesive between the HDPE matrix and the dispersed phase. In the presence of 10% by weight of LDPE-g-DBAE as a compatibilizer, more fine particles and a dim phase interface were observed, and the blends showed a remarkable increase in heat distortion temperature and mechanical properties. The compatibilized blends possessed a high apparent viscosity as compared with the noncompatibilized ones. However, the apparent viscosity of the blends, with or without the compatibilizer, was lower than that of the neat HDPE and PC. Exploration by DSC found that the melting point and the crystallinity of HDPE in the blends decreased, and especially for the blends with the compatibilizer. These facts could be interpret ed in terms of the efficient compatible effect of the LDPE-g-DBAE, which resulted from the interaction between, the diallyl bisphenol A ether unit of LDPE-g-DBAE and polycarbonate, and the miscibility of the LDPE unit and HDPE.