Abstract: Automatic gain control (AGC) is a modulus commonly used in seismic data processing. The paper, through building model and two processing flowcharts, analyzed shot gather, CDP gather and the influence of the use of the modulus after data stacking on amplitude, then discussed the influence of the modulus on amplitude interpretation technology such as AVO attribute analysis, identification of lithology and fluid. In the study, it was considered that AGC would bring sever falsification of the amplitude at lithologic anormaly, inducing misinterpretation. In the processing flowchart with amplitude interpretation as objective, it is forbidden to utilize AGC before and after stacking.