Window solar air collector is a significant instrument for heating residential buildings in cold regions. This paper presents an experimental investigation of the thermal performance of a window solar air collector with seven moveable absorber plates, as each plate contains 28 circular perforations. The 7 plates opened and closed at different angles in unison manually by a specific mechanical mechanism. The effect of changing the plate angles have been tested, alongside the effect of mass flow rates and the intensity of solar radiation. Experimental results shows that the highest air temperature difference is gained at vertical plates position (angle 0) at mass flow rate 0.0097 kg/s and irradiance 730 W/m 2, and the maximum thermal efficiency were 71% at mass flow rate 0.0224 kg/s. In addition, the temperature difference between inlet and outlet air has increased by 24% in case of angle 0 than in angle 45. In contrast, a flexibility between sunlight penetrating into the room and hot air from the collector will be gained when the plates set on angle 45.