This study presents a numerical investigation on heat transfer enhancement of mixed convective how in a horizontal block-heated channel. The heat transfer enhancement in this study has been accomplished by the installation of an oblique plate for internal flow modification induced by vortex shedding. The oblique angle of the plate is changed (30-90 degrees) under Reynolds numbers (260-530) and Grashof numbers (0-3 200 000) for the purpose of investigating the heat transfer performance. The results show that the installation of an oblique plate in cross-flow above an upstream block can effectively enhance the heat transfer performance of mixed convection in the horizontal channel flow.