Abstract: Aiming at the counter of intermittent sampling repeater interference, the matched filtering process was re-examined based on the tools of geometric algebra. Furthermore, the geometric matched filter is proposed with the complementary angle of the projection angle as its output. Then, the geometric matched filter’s response characteristics to intermittent sampling repeater interference are analyzed. The geometric matched filter is applied to estimate the duty of the interference, which provides a priori knowledge for the suppression of the interference Meanwhile, several simulations confirm that the geometric matched filter overperforms in the adaptability to the background of strong interference and the target detection. The presented results provide a new geometric perspective for the counter of slicing forward jamming.