Flow and heat transfer characteristics of a channel with oblique plates which are mounted periodically on the channel wall have been numerically investigated in a laminar range. The main objective of the present study is to find the effect of the tilt angle of oblique plate on pressure drop and heat transfer characteristics in unsteady states. To get the different conditions of the heat transfer and flow evolution, two key parameters of the Reynolds number and the tilt angle of oblique plate are considered. At R_e=200,600, the tilt angles are changed for the range of 50° - 130°. The computational results show that the heat transfer and pressure drop are strongly dependent on the tile angle and Reynolds number. When the flows are unsteady, the tilt angle has an important role in the heat transfer enhancement. Oscillatory structures induce the better mixing of the thermal field and promote the wall heat transfer. For a constant plate length, the wall heat trans- fer is maximized near the 90° - 100°. This is strongly coupled with the variations of flow mixing induced by the oblique plate.