Abstract: In order to investigate the influence of sinusoidal bottom wall structure on the flow and heat transfer characteristics,five types of microchannel with sinusoidal bottom wall(MCSBW)were designed.The numerical simulation method was used to study the local flow and heat transfer performances in these microchannels at Reynolds numbers of 530 and 1 060.Results showed that the secondary flow appears in the MCSBW.The local pressure,Poiseuille number,wall temperature and Nusselt number along flow direction presented a fluctuated trend in the MCSBW,but the latter two were slight.In the range of Reynolds number(230~1 060),the average Poiseuille number of sinusoidal microchannels increases with the increase of Reynolds number.When the Reynolds number of sinusoidal microchannels is less than 600,the average Nusselt number is slightly lower than that of smooth microchannels,which indicates that the heat transfer effect is deteriorated.When the Reynolds number is greater than 600,all the average Nusselt number of sinusoidal channel is larger than that of smooth channel,which indicates that the heat transfer effect is better.