The invention discloses a method and system for generating random noise of a forward modeling seismic record, and belongs to the technical field of data processing of seismic prospecting. In the aspect of forward modeling, a common midpoint (CMP) trace gather with a complex random interference background is constructed rapidly on the basis of a random interference typical decomposition method; andin the aspect of superposition of the CMP trace gather, the CMP trace gather is superposed by taking a probability statistical property of the random interference background as the basis to realize optimal superposition. A simulated record with the interference background is compared with a record collected practically in the field, the seismic wave field of a region with complex construction andland surface can be understood more, a processing result of the record, with low signal-to-noise-ratio, with the interference background is compared with a processing result without the interferencebackground for analysis, verification data is provided for research on different processing methods, and collection, processing and interpretation of practical data are guided.