Experimental trials conducted from 2003 to 2005 in cast China sea demonstrated that HF surface wave radar (HFSWR) OSMAR (Ocean State Monitor and Analysis Radar) could be strongly affected by scattering from ionospheric structures and irregularities. A large database acquired during those trials has been used in detailed investigations of the phenomenology of this ionospheric clutter, leading to the development of effective mitigation techniques based on the characteristics of ionospheric clutter. In this paper the 2-D angle of arrival of ionospheric clutter has been analyzed and the spatial adaptive processing based on 2-D antenna array is introduced to suppress ionospheric clutter. Experimental results confirm that the above technique can achieve effective ionospheric clutter suppression using the field experimental data recorded by the OSMAR2003.