Abstract: Experiments on friction factor and heat transfer performances are conducted in a trapezoidal silicon microchannel heat sink with deionized water as working fluid.The flow and heat transfer parameters are obtained in different volume flowrate and different heat flux,along with simultaneous measurement of the pressure and temperature.It is found that the heat transfer characteristics in trapezoidal silicon microchannels deviated from theoretical predictions for conventional channels.The corner between the side wall and the bottom wall has an significant influence on the flow and heat transfer performances.Based on the test results,a modified relation for the heat transfer characteristics of trapezoidal silicon microchannel heat sink is obtained.