The　insufficiency　of　single-flank　testing　is　analyzed.　Today＇s　solutions　and　their　existing　problems　are　discussed.　Based　on　this,　the　gear　pair　integration　error　(GPIE)　is　used　to　efficiently　eliminate　the　insufficiency　of　the　single-flank　testing.　GPIE　takes　all　errors　of　a　gear　pair　as　a　set,　and　this　set　is　represented　by　the　gear　pair　integration　error　curve　(GPIEC)　which　is　formed　in　the　way　that　the　deviations　of　all　points　on　conjugate　tooth　flanks　of　the　gear　pair　are　marked　with　the　same　base　zero　and　are　arranged　along　the　action　line　of　the　gear　according　to　the　meshing　sequence　of　the　correspondent　mesh　points.　An　introduction　of　the　deduction　of　this　theory　and　its　definition　formula,　as　well　as　the　synthesis　method　of　the　GPIEC　are　presented.　Finally,　the　feasibility　and　efficiency　of　the　theory　are　demonstrated　in　resolving　the　insufficiency　of　the　single-flank　testing　and　analyzing　the　sources　of　transmission　quality　and　gear　noise　through　the　comparison　between　the　GPIEC　of　a　gear　pair　and　its　transmission　error　curve.　The　significance　of　the　theory　are　summarized　with　respect　to　their　influence　upon　formulating　standards　for　gear　tolerance,　analyzing　errors　of　gear-cutting　machines　and　transmission　quality　of　the　gear　pair,　and　innovating　ways　to　the　research　of　the　dynamic　characteristics　of　gears　and　their　noise.