When　a　power　apparatus　is　put　into　operation,　temperature　difference　always　exists　in　its　insulation.　As　to　HVDC　insulation　system,　this　temperature　gradient　may　play　an　important　role　on　the　space　charge　behavior　and　field　distribution.　This　report　summarized　our　attempts　to　understand　the　effects　of　temperature　gradient　on　space　charge　and　material　lifetime.　Modified　pulsed　electro-acoustic　(PEA)　measurement　systems　and　corresponding　waveform　recovery　algorithms　applicable　to　temperature　gradient　for　film　samples　and　coaxial　cables　were　developed.　Space　charge　behaviors　under　different　temperature　gradients　of　film　samples,　like　LDPE,　oil-paper　and　epoxy　resin,　as　well　as　of　coaxial　cable　were　compared.　Moreover,　a　bipolar　charge　transport　model　was　used　to　elucidate　these　phenomena　and　study　the　mechanism　of　space　charge　behavior　under　temperature　gradient.　It　was　concluded　that　conductivity　gradient　caused　by　temperature　gradient　across　the　bulk　and　the　different　injection　and　extraction　behavior　of　charges　due　to　temperature　difference　of　two　electrodes　brought　up　the　different　experimental　results.　Furthermore,　step　voltage　test　was　carried　out　to　study　the　aging　law　of　XLPE.　The　obvious　increase　of　aging　exponent　under　temperature　gradient　was　attributed　to　the　hetero-charge　accumulation,　which　increased　rapidly　with　electrical　field　and　thus　greatly　enhanced　the　field　distortion　and　recombination　density　in　the　adjacent　of　low-temperature　electrode.