Abstract: The solid temperature field and the effect of heat conduction mechanism of the solid on heat transfer near the corner in a narrow rectangular channel are required to further understand when the un-heating region is optimized. The liquid-solid conjugate heat transfer in a narrow rectangular channel was numerical analyzed by using CFD code CFX. The results show that the heating concentration phenomenon can be avoided when the un-heating region of 1 mm×2 mm near the corner is designed, and the effect of un-heating region on temperature field at the channel center is negligible. The distributions of inside wall heat flux and temperature are not uniform when heat conduction boundary condition of the solid near the un-heating region is set. The temperature of the solid in un-heating region is enhanced because of metal heat conduction, which contributes to enhance liquid temperature near the region. The effect of constant volume heat flux and constant wall heat flux on heat transfer is negligible when adiabatic boundary condition of solid near the un-heating region is set.