This　study　proposes　an　improved　microchannel　heat　sink　with　offset　zigzag　cavities　to　enhance　boiling　performance.　Flow　and　heat　transfer　characteristics　are　experimentally　investigated　via　a　microscale　boiling　heat　transfer　visualization　system　using　acetone　as　the　working　fluid.　At　mass　fluxes　of　285,　402,　and　684　kg/(m(2).s)　and　heat　fluxes　of　1.31-80.26　W/cm(2),　the　effects　of　heat　and　mass　fluxes　on　flow　pattern,　heat　transfer,　wall　temperature,　and　pressure　drop　of　zigzag　microchannel　heat　sink　are　analyzed　and　compared　with　conventional　rectangle　microchannel　heat　sink.　Results　show　that　the　fluctuating　amplitude　first　increases　and　then　decreases　with　the　increment　of　heat　fluxes,　thereby　causing　a　quasi-steady　and　unstable　boiling　with　small　fluctuations.　Instability　becomes　increasingly　severe　for　the　nucleate　boiling　area　moves　toward　the　inlet　and　flow　reversal　intensity　increases　with　heat　fluxes　under　low　heat　flux.　With　heat　flux　increased　furtherly.　The　proportion　of　steam　in　the　channel　increases　to　reduce　fluctuations.　Compared　with　the　rectangular　microchannel,　the　zigzag　microchannel　evidently　enhances　heat　transfer　characteristic　with　lower　wall　temperature　at　the　onset　of　nucleate　boiling　(ONB),　higher　heat　transfer　coefficient　(HTC)　and　critical　heat　flux　(CHF)　and　improves　boiling　stability　by　suppressing　flow　reversal　and　reducing　two-phase　pressure　drop.　The　mechanism　of　zigzag　microchannel　enhancement　boiling　performance　can　be　attributed　to　(1)　the　improved　disturbance　of　the　working　fluid,　which　enhances　forced　convective　boiling　heat　transfer　and　mitigates　bubble　coalescence　and　flow　reversal　strength;　(2)　the　continuously　developing　liquid　film　and　improved　wettability　maintain　a　stable　liquid　film　evaporation　and　delay　partial　dry　out.　Increase　in　mass　flux　can　improve　CHF　and　reduce　pressure　drop　albeit　with　high　wall　temperature　of　ONB.　The　local　HTC　is　enhanced,　except　for　the　low　heat　fluxes,　because　the　bubbles　are　condensed　by　liquid　and　cannot　grow　to　absorb　heat　at　low　heat　fluxes.