Abstract: The origin and the age of many ancient marine eroded landforms in the coastal areas of Guangdong cannot be determined due largely to no sediments kept with or within the landforms. Arguments about the origin for the marine eroded landforms are, therefore, often raised by the fact that non-marine eroded landforms also have similar morphological features. The difference between marine and non-marine eroded landforms is originally caused by the different erosion processes resulting in the different morphological features, although, some of which are similar. The focus of this study is trying to highlight a number of such differences important for distinguishing marine eroded landforms from non-marine ones. Ancient marine landforms found at Huangpu. Town is one with typical marine eroded features. In this article, morphological features of the ancient marine landforms at Huangpu were compared to those with similar features but formed from non-marine origin. The difference among those feature and their origins are analyzed based on the principles of dynamical geomorphology. The comparison indicates: (1) Ancient marine notches or caves associated with marine benches only appeared at a same horizontal level such as the hill foot that was a formal sea-level, and could cut off both hard and soft rock layers along this level. (2) Differential weathering or erosion by sheet flows on a hill slope with structural difference would produce notch-like features or grooves along the soft rock layers or the structural weaknesses of the slope, no matter they were horizontal or not. The notch like features could develop all the way from the top to the foot of the hill slope but without any benches formed in front of the grooves. (3) The lateral erosion of a river is also horizontal but could not produce notches and benches at the same time. (4) The dissolution process of river water was also horizontal, by which horizontal grooves were formed in limestone river banks at the height of the water surface. A prominent roof could often formed over the groove but no benches formed in front of it because of more dissolution under the water than in the air. (5) By the same reason, marine notches without marine platforms or benches developed on limestone coasts with short fetches. (6) The width of the marine bench apparently increased with greater wave energy.