Micro-cracks　produced　in　the　crushing　stage　could　improve　the　permeability　and　diffusion　of　leaching　solution　within　the　ore　particles,　which　would　favor　for　the　leaching　process.　However,　its　influence　on　the　extraction　of　copper　by　bioleaching　has　rarely　been　studied.　In　this　work,　we　reported　the　enhancement　effect　of　micro-cracks　on　the　bioleaching　of　low-grade　copper　sulphide　ore.　Jaw　crusher　and　high-pressure　grinding　rolls　were　adopted　to　prepare　ore　samples　of　the　same　size　fraction　but　with　different　number　of　micro-cracks　in　the　ore　particles.　Statistical　data,　scanning　electron　microscope　(SEM)　and　stereomicroscopy　(SM)　images　clearly　showed　that　high-pressure　grinding　rolls　could　generate　more　and　larger　micro-cracks　than　the　same　produced　by　jaw　crusher.　Subsamples　from　the　−0.9　mm　and　3–6　mm　size　fractions　were　utilized　for　shake　flask　and　column　bioleaching　experiments,　respectively.　The　earlier　change　in　pH　and　higher　oxidation-reduction　potential　(Eh)　indicated　that　more　micro-cracks　were　beneficial　for　the　growth　of　bacteria,　which　then　enhanced　the　bioleaching　efficiency　of　copper.　In　the　shake　flask　experiments,　the　copper　extraction　efficiency　was　increased　from　87.4%　to　94.3%　on　the　30th　day　at　40　°C　and　150　rpm.　Similarly,　in　the　column　experiment　with　the　ore　sample　prepared　by　high-pressure　grinding　rolls,　an　approximately　12.2%　improvement　of　bioleaching　efficiency　was　observed　as　compared　to　the　system　with　the　ore　sample　prepared　by　jaw　crusher.　These　results　demonstrated　that　creating　micro-cracks　could　be　crucial　for　heap　bioleaching　of　low-grade　copper　sulphide　ores.　©　2019　Elsevier　B.V.