A novel absorption band-pass filter (ABF) with wide relative bandwidth and compact structure is proposed and investigated. The ABF consists of two identical 3dB directional coupler (DTC) and two identical reflecting band-pass filters (RBF), which are all based on Microstrip line structure. Firstly, Compared with conventional LC filter, this novel filter has higher passband frequency, broader relative bandwidth and 3dB bandwidth, due to the application of Microstrip line structure. Secondly, the structure of the device is compact and designed simply, it has low cost and can be easily integrated with the active devices. Finally, we get a novel ABF with good performance: the center frequency is 4GHz, the 3dB bandwidth of the ABF is 745MHz, the insertion loss in passband is less than 3dB, the voltage standing wave ratio (VSWR) is less than 1.7 in passband, the relative bandwidth is 18.625%.