Abstract: This paper studies a new microstrip hairpin bandpass filter by using ADS (Advanced Design System). The filter is used in Sband. Compared to the conventional microstrip hairpin bandpass filter, microstrip lines of a quarter wavelength are added in both input and output of the filter, which provides great suppression of parasitic passband. A microstrip line is also added between non-adjacent resonators of the hairpin bandpass filter, which makes the filter has a pair of transmission zeros around the passband. Finally, the designed filter is made for testing, and the testing results show a good agreement with the simulated results.