The　full-slime　cyaniding　leaching　experiments　of　fine　particles　products　crushed　by　conventional　jaw　crusher　and　high　pressure　grinding　rolls　(HPGR)　were　conducted,　the　influences　of　two　different　comminuting　processes　on　the　leaching　rate　of　low　grade　gold　ore　processed　were　studied.　Combined　with　the　particle　surface　test　results　and　scanning　electron　microscopy,　the　mechanism　of　HPGR　in　the　treatment　process　of　gold　ore　was　studied　furthermore.　The　result　shows　that　the　products　of　HPGR　are　finer　but　not　more　uniform　than　that　of　conventional　jaw　crusher.　The　gold　leaching　rate　of　less　than　0.15　mm　part　under　the　same　conditions　can　be　increased　by　3.7%-6.6%.　The　number　and　size　of　micro-cracks　from　this　two　comminuting　process　become　obvious　difference.　HPGR　can　produce　richer　micro-cracks　through　the　quasi-static　pressure,　which　contributes　to　the　penetration　of　leaching　reagents　through　the　cracks.　On　the　other　hand,　the　specific　surface　area　and　porosity　of　particles　increase,　which　will　be　beneficial　to　the　contact　of　gold　and　leaching　reagents.　So　the　mechanism　of　influences　on　the　gold　leaching　rate　of　different　comminuting　process　in　theory　can　be　revealed.　©　2016,　Central　South　University　of　Technology.　All　right　reserved.