Th　e　SHG　tolerance　characteristics　of　PPRTA　crystals　have　been　theoretically　analyzed　based　on　the　QPM　theory.　And　the　theoretical　tolerance　tuning　curves　of　PPRTA　crystals,　including　such　tolerance　parameters　as　polar　inversion　grating　period,　temperature　and　fundamental　wavelength　etc,　have　been　simulated　and　compared　with　PPKTP　and　PPLN　crystals.　The　tolerance　parameter　maximum　of　PPRTA　such　as　polar　inversion　grating　period　ΔΛ,　temperature　Δtmax,　and　Δλωmax　of　PPLN　for　the　corresponding　fundamental　wavelength　in　the　same　conditions　is　2.743　3　μm,　2.247　4　μm,　and　2.704　6　μm,　respectively.　The　conclusionis　is　that　the　theoretical　result　provides　bases　for　the　QPM-SHG　experiment　of　periodically　poled　crystals.