Abstract: Based on the configuration of traditional triangle bandpass filter, a new dual-mode bandpass filter using an isosceles triangle patch resonator with slot is presented in this article. The isosceles triangular patch resonator has a T-shaped slot in it, and its parameters are optimized. The optimized filter has two zero-transmission points on both sides of the pass-band so as to improve its rejecting ability of stopband. Also the structure of the filter is miniaturized. Simulation of the presented filter found that the central frequency of its pass-band is at 5 GHz. It is confirmed that the experiment is in good agreement with simulated results.