In this paper, a dual-band bandpass filter with low insertion loss in the pass bands and compact size is designed using only two open-loop microstrip resonators loaded by in-line beelines. The in-line beelines, are loaded to achieve two passbands with high performance. By adjusting the stub lengths and widths and also the tap line position, the harmonics above the second band are supperssed. The minimum insertion loss is 0.9 and 0.2dB at the first and second passbands respectively. The minimum attenuation above the second passband is -19.5dB from 5.4 up to more than 20GHz, so it can be used for wideband applications. This filter is then fabricated and measured. The measured and simulated results are in good agreement.