Abstract:Weak reflection is a reflection phenomenon we can often see in seismic section. The weak reflection is usually considered to come from single-lithologic formation in predicting lithology. The seismic example in Liaodong bay has shown that weak reflection can mirror single-lithologic formation, or mufti-lithologic formations: the formation that is composed of thin interbeds,and the formation consisting of thick sandstone and mudstone layers which have very low reflection coefficients. With the use of geological model, the author expounds how the weak reflections occur and how they can be distinguished. It is emphasized that the lithology of weak reflection configuration in continental sedimentary basin is determined not only by consulting some interpretation patterns but also by performing comprehensive analysis of various seismic informations, sedimentary feature and stuctural feture in the area.