To　understand　the　residual　stress　distribution　in　the　welded　joints　of　high　density　polyethylene　(HDPE)　pipes　is　essential　to　the　assessment　of　its　structural　integrity.　However,　limited　knowledge　of　their　residual　stress　was　available　in　this　regard.　In　this　paper,　the　hole-drilling　strain-gage　method　was　used　to　measure　the　residual　stress　in　the　welded　seam　of　HDPE　pipes,　which　was　produced　by　the　butt　fusion　welding　technique.　The　finite　element　modeling　using　viscoelastic　constitutive　model　with　Prony　series　was　carried　out　to　determine　the　temperature　field　and　corresponding　stress　field　in　the　welding　stages.　The　measured　residual　stress　near　the　surface　shows　good　consistency　with　the　numerical　results.　It　is　shown　that　the　residual　stress　in　the　hoop　direction　is　much　larger　than　those　in　the　radial　and　axial　directions.　The　effect　of　the　pipe　thickness　on　the　residual　stress　distribution　was　also　investigated　by　numerical　simulation.　The　positions　of　the　maximum　tensile　stress　in　the　welded　joints　were　found　within　the　normalized　depth　region　(the　radial　depth　to　the　thickness)　of　0.2　to　0.8.