We present the design of a compact dual-band bandpass filter using open-loop resonator, which connected together with mixed coupling, loaded by T- shape stub and open stubs. Open stubs are loaded to achieve high performance and the tapped line feed structure is used in input-output port. By adjusting the tapping position, stubs length and the impedance ratio of T- shape stub, the filter performance can be controlled. The T shape stubs are used to suppress the harmonics above the second band. The insertion losses are 0.2dB and 0.9dB at 2.7 and 5GHz respectively. Above the second pass band minimum attenuation is -20dB from 5.3 to 20GHz, so it can be used for ultra wide stopband applications. The measurement results have shown a good agreement with the simulation.