WithvonMisesyieldcriterion,theloadingrangeofNetSectionCollapse(NSC)Criteriaisextendedfromcombinedtensionandbendingloadingstocombinedbending,torsionandinternalpressureloadings.AnewtheoreticalanalyzingmethodofplasticlimitloadforpressurepipewithincompleteweldingdefectsbasedontheextendedNSCCriteriaispresentedandthecorrelativeformulasarededuced,theinfluencesofpipecurvature,circumferentiallengthanddepthofincompleteweldingdefectsontheplasticlimitloadofpressurepipeareconsideredaswellinthismethod.Meanwhile,accordingtotheorthogonalexperimentaldesignmethod,theplasticlimitloadsarecalculatedbythefiniteelementmethodandcomparedwiththetheoreticalvalues.Theresultsshowthattheexpressionsofplasticlimitloadofpressurepipewithincompleteweldingdefectsunderbending,torsionandinternalpressurebasedonextendedNSCcriteriaarereliable.Thestudyprovidesanimportanttheoreticalbasisfortheestablishmentofsafetyassessmentmeasuretowardspressurepipewithincompleteweldingdefects.