Interesting　in　generation　and　exploration　of　mid-infrared　radiation　has　induced　using　optical　parametric　effect　in　nonlinear　optical　crystal　with　high　nonlinearity,　high　transmission,　phase-matching　ability,　and　high　sensitivity　in　room　temperature,　such　as　AgGaSe2(AGSe),　AgGaS2(AGS)　crystals.　To　achieve　mid-infrared　radiation,　we　use　difference　frequency　generation　(DFG)　in　AGS　or　AGSe　crystals　by　pumping　with　the　output　of　optical　parametric　oscillator.　The　mid-infrared　radiation　tunable　characteristics　of　AGS　and　AGSe　crystals　under　type-I　phase-matching　have　been　analyzed　based　on　optical　parameter　DFG　theory.　Beam　walk-off　angle　and　acceptance　angle　limit　conversion　efficiency　and　restrict　the　DFG　tuning　wavelength　range.　We　focus　to　research　for　effective　nonlinear　coefficient,　walk-off　angle　and　acceptance　angle　as　functions　of　wavelength,　the　relationship　between　conversion　efficiency　and　acceptance　angle,　and　crystals　length　impact　on　the　process　of　frequency　conversion.　We　obtained　10　mu　m　wavelength　with　a　10　mm　crystal　length,　1030nm　pump,　walk-off　angles　and　acceptance　angles　of　AGS　and　AGSe　crystals　are　1.19　degrees　and　0.68　degrees,　0.107　degrees　and　0.171　degrees　respectively.　Results　are　very　useful　for　mid-infrared　experimental　studies　on　AgGaS2　and　AgGaSe2　crystals.