We report on the design, the fabrication and the measurement of a microwave dual band absorber in microwave regime. The single unit cell consists of two closed ring resonators and a metallic ground plane separated by an FR4 layer. Experimental results show that the absorber has two distinctive absorption peaks at frequencies 4.06 GHz and 6.66 GHz with absorptions 99.60% and 95.83%, respectively, and the absorptivity drops in a wide range of incident angle. Fourfold rotational symmetry of the geometry makes the absorber insensitive to transverse electric and transverse magnetic polarization. The dual band absorber is a promising candidate as absorbing elements in multi-frequency imaging and thermal detection, due to its multi-band absorption performance, polarization-insensitivity, and wide angle of incidence.