With the increasing output power of the integrated circuit chips, the heat flux involved is being accordingly increased. In such situation, the air has almost reached its limit of cooling capacity, and thus the liquid cooling technology incorporating microchannel heat sinks is desired to cool the electronic chips in order to remove more heat loads. However, these microchannel heat sinks are often designed to be straight with rectangular cross section. In this study, on the basis of a straight microchannel having rectangular cross section, a kind of transversal wavy microchannel is designed and then the laminar flow and heat transfer are investigated numerically. It is shown that for removing the identical load, the transversal wavy microchannel has great potential to reduce pressure drop compared to the straight microchannel, especially for higher wave amplitude at the same Reynolds number, indicating the overall thermal performance of the transversal wavy microchannel is superior to the traditional straight rectangular microchannel. It is suggested such wavy microchannel can be used to cool chips effectively with much smaller pressure drop penalty.