Experiments were performed to evaluate the micro-scale flow boiling heat transfer characteristics of acetone flowing through triangular silicon microchannels.The liquid-vapor two-phase flow pattern was visualized，along with simultaneous measurement of pressure and temperature.Periodical convective boiling heat transfer in a time scale of milliseconds was found.A full cycle can be subdivided into three sub-stages：liquid refilling stage，bubble nucleation，growth，coalescence and explosion stage，and transient liquid film evaporation stage.The flow field visualization showed that four liquid-vapor two-phase flow patterns appeared in microchannels，and the boiling incipience was identified.The effect of mass quality（x）on boiling heat transfer coefficient was analyzed.It was shown that under the conditions of the present study，when x <0.4，nucleate boiling was dominant，whereas when x >0.4，the forced convective boiling was dominant.