Abstract: Multiples is one of common noises in seismic exploration, the techniques of multiples attenuation is a serious problem in seismic data processing. This paper introduced the formations, classifications, characteristics of multiples, and the multiples attenuation in synthetic seismic data in ProMax system. Firstly, NMO correction with the appropriate speed for CDP gathers in t-x domain; Secondly, used F-K transform and Radon transform respectively to convert it to different domains, then attenuated the area where multiples was in new domains; Finally, transformed it to t-x domian through the corresponding inverse transforms to achieve the purposes of the multiples attenuation. By the applying of multiples attenuation in ProMax system, it suggests that different methods of multiples attenuation have advantages and disadvantages, and multiples attenuation in combination with different methods will achieve better results.