The invention discloses a three-passband micro-band filter with low loss, based on a wedged SIR (Signal to Interference Ratio) structure. The three-passband micro-band filter adopts a coupling feedback structure on a micro-band transmission line with matched 50ohm resistance, and a rectangular defective geo-structure (DGS) is additionally arranged under the lower side of the three-passband micro-band filter; and a resonator adopts an interdigital wedged SIR (Signal to Interference Ratio) structure. The wedged SIR structure adopts a transition line for improving the resistance mutation of the SIR to achieve the smooth effect, and can be equivalent to a limiting form of a multi-order SIR at the same time, and the coupling effect is stronger. The rectangular defective geo-structure (DGS) additionally arranged under 50ohm of a coupling feeder line is equivalent to that one low-pass filter is cascaded at the front end of a post-stage band-pass filter, thereby the performance of the filter under the condition of not increasing the volume of the filter is further optimized. The invention discloses the three-passband micro-band filter with the low loss on the basis of the wedged SIR structure, the structure of the which is smaller than that of a single filter, and the three-passband micro-band filter can better meet the requirement on modern communication of miniaturized three-passband.