In the present paper, we carried out a numerical investigation on the effect of pulsating inlet on the heat transfer performance in a manifold microchannel heat sink.Three types of pulsating inlet condition were examined in order to gain a better thermal performance, including square wave, cosine wave and semi-cosine wave.The attentions were then paid to parametric effect of the pulsating inlei condition including the pulsating amplitude and duty ratio which describe the pulsating pattern.The results showed that introducing pulsating flow could significantly improve the heat transfer performance comparing with that of steady flow under the same mass flow rate and action time.Moreover, the pulsating inlet with cosine wave led to higher heat transfer coefficient among the three types of pulsating inlet conditions in consideration.