Abstract: A novel compact microstrip low-pass filter with wideband suppression is proposed in this paper. The filter is composed of defect ground structure (DGS) and stepped impedance structure unit. The model was built and optimized by ANSYS HFSS. The simulation results show that the cut-off frequency of the low-pass filter is 1.4 GHz, the passband width is 0-1.4 GHz, the insertion loss in the passband is less than 0.5 dB, the out-of-band rejection frequency width is from 2.1 GHz to 11 GHz, and the out-of-band rejection in the stopband range is about 20 dB. In order to verify the test results and simulation results, an optimized defect-structured microstrip low-pass filter was processed and tested. The practical measurement are in good agreement with the simulation results. It is proved that the defect ground structure plays an important role in realizing the miniaturization of the filter and the wide impedance bandwidth. Moreover, the defect ground structure provides better low-pass filtering characteristics to the filter.