According　to　the　Sellmeier　dispersion　equation　and　law　of　energy　conservation　and　momentum　conservation,　the　tuning　characteristics,　conversion　efficiency,　permitted　parametric　and　walk-off　effect　of　ZGP-DFG　have　been　obtained　using　numerical　simulation　in　type-I　and　type-II　phase-matched.　The　ranges　of　angle　tuning　were　51°~89°　in　type-I,　and　58°~88°　in　type-II.　The　corresponding　ranges　of　wavelength　were　3.1~12　μm　and　6.2~11.5　μm,　respectively.　In　addition,　the　corresponding　characteristics　of　AgGaS2　(AGS)　and　AgGaSe2　(AGSe)　were　compared　with　ZGP,　and　the　conclusion　was　the　walk-off　effect　of　ZGP-DFG　was　small,　and　the　conversion　efficiency　of　ZGP-DFG　was　the　highest　among　the　three　crystals.　In　summary,　ZGP　was　a　better　crystal　to　produce　the　mid-infrared　laser.