Space-charge distributions in plate and coaxial cable samples of various polyethylene (PE) materials such as high density polyethylene, linear low density polyethylene, low density polyethylene, and cross-linking polyethylene under dc voltage are systematically investigated by the pulsed electro-acoustic method. The chemical structure and morphology of the sample materials are studied. The formation mechanism of space charge and the relations among space charge, chemical structure, and morphology are discussed. Our research results show that the distribution characteristics of space charge in various PE materials can be attributed to their chemical structure and morphology.