A novel split ring and complementary split ring resonator is proposed in this letter.The proposed resonator can generate two notches without increasing the physical size. A microstrip lowpass filter (LPF) is designed based on the proposed resonator. The cutoff frequency of the designed LPF is 3.7 GHz and the stopband with an attenuation level lower than -20 dB is obtained from 3.9 to 7.5 GHz. The selectivity is calculated to be 85 dB/GHz. The physical size of the LPF with transmission lines is 29 × 6 mm 2. A good agreement between simulated and measured results is achieved.