The invention discloses a method for determining effective excitation points on the basis of illumination energy of target strata during geophysical prospecting for petroleum. The method includes designing an observation system for the target strata; performing forward modeling on the observation system after shots are infilled in the observation system; acquiring illumination energy generated by each shot for each surface element on the target strata; determining positions of the surface elements with the minimum energy; computing illumination energy of each shot in a standby shot point set for areas with the minimum energy according to average value and distance energy ratios; determining the effective excitation points to select infill shot points according to average variance of the illumination energy of shots in a shot set for the target strata. Shot points selected from the standby shot point set are added into an effective excitation point set to form the shot set. The method has the advantages that the observation system can be effectively arranged in areas with high steep structures, overthrust nappe structures and structures with violent speed horizontal change, the illumination intensity of shadow areas can be improved by the minimum effective excitation points, and the quality of seismic sections can be improved.