Abstract: High frequency surface wave radar (HFSWR) is an ideal early-warn ing radar, but its detection performance is severely affected by the ionospheric clutter. Ionospheric reflection to radar signals and Doppler broadening is ana lyzed theoretically in this paper. The statistical properties of the ionospheric clutter ampli tude and power spectrum amplitude are researched based on the experimental data. The time and range correlation characteristics of ionospheric clutter are stu died and analyzed through the ionosphere configuration. It is useful in ionosphe ric suppression, HFSWR optimization design and low speed target detection.