Abstract: The abnormal noises, such as burst pulse, electricity inflection, and interference of 50Hz industrial frequency, are common in prestack seismic data. Their energy, frequencies, and dispositions are different from that of seismic signals. This paper illustrates with both synthetic and real data that the impact of the abnormal noises to prestack multichannel processing can not be ignored. It is necessary to do detailed analysis on prestack data and perform effective noise suppression to guarantee the quality of data processing.