Abstract: The drilling of well X in S281 block of Damintun sag, Liaohe depression, shows a great oil and gas potential. However, it is difficult to determine the main fault position and microfracture system due to the old acquisition time of previous seismic data, low coverage times and poor imaging precision, which restricts the interpretation of block accumulation and subsequent development. Therefore, the study carries out the high density wide line 2D seismic data acquisition and degradation analysis of the observation system based on the data. The results show that, compared with the previous 3D seismic imaging section, the newly acquired high density wide line 2D seismic imaging section has clearer breakpoints, clearer delineation of fault system, more natural structural configuration, richer interlayer information, and higher signal-to-noise ratio, which accurately realizes the structural characteristics of western slope zone. The ultrahigh density and minimum bin can depict high-steep structures and faults more clearly, which is an effective method to improve the imaging of complex geological targets. The degradation processing indicates that the bin side length of seismic data acquisition and observation system of S281 block should not be greater than 12.5 m, the maximum offset should not be less than 3 500 m, and the coverage times should not be less than 1 200 times. The study can provide reference for the next seismic data acquisition and exploration in the western slope zone of Damintun sag.