The Panyu low uplift of Pearl River Mouth Basin is a favorable accumulation area of hydrocarbon. Many structures have shallow gas with changeable thickness. This influences the time depth conversion of the major gas pools deep below greatly. According to the characteristics of gas pools, this paper analyses shallow gas from its formation mechanism, forward modeling and seismic section characteristics, and then eliminates the influence of shallow gas by time correction method. This method is economical and valid in practice.