Some features in late coda correlations have now been commonly treated as “the inter- station body waves”. In general, however, large earthquakes releasing coda waves mostly situate at the continental boundaries. It remains unclear as to how such a discrete and non- uniform distribution of earthquakes influences these features. To understand the impacts, here we introduce geometric ray theory to explore the body wave cross-correlation. In the stationary phase integral, we show that the distribution geometry of earthquakes and the dimension of the stationary phase zone significantly influence the correlation phases. The dimension of the stationary phase zone is inversely proportional to the k-κ coefficient which, as a newly-proposed terminology, is composed of the seismic wave-number and the coda propagation distance. In late coda correlations, most of the large earthquakes situate in the stationary phase zone for constructing the inter-station wave due to the small k- κ coefficient. However, because earthquakes are not always at the stationary points, the correlation signals may appear a little earlier than their counterparts in Green’s function. We have verified the theoretical analyses with the synthetic and realistic coda correlations.This theory is also applicable in other physics fields allowing for geometric ray theory. It demonstrates that the event-receiver geometry can result in the travel time variation up to 1/6 of the body wave correlation period. Thus, researchers should carefully investigate the impacts when utilizing the correlation signals as inter-station body waves for the future work of illuminating the Earth’s discontinuities.