Fluvial reservoir of the upper Guantao Formation in Guandong Oilfield is an important oil-bearing strata, and the characteristics and scale of sand bodies in the late development of the old oilfield need a fine characterization. The sedimentary characteristics and evolution model from braided fluvial to meandering fluvial deposit were determined based on the analysis of facies markers such as core, logging, and seismic. The braided fluvial reservoir develops braid bar, braid channel, and overbank sand microfacies at the lower part of upper Guantao Formation. Meandering fluvial reservoir develops point bar, abandoned channel, crevasse splay, and floodplain are developed microfacies at the upper part of upper Guantao Formation. Through core-log calibration analysis, the logging response characteristics and sandbody development law of braided and meandering river are determined. The braided fluvial channel sand bodies are stacked in multiple stages, and are distributed in multiple branches in the plane. The meandering river channel sand bodies develop in isolation with a strip shape in the plane. Under the control of dense well array, the scale of braided and meandering river sand body was determined, and the sedimentary evolution process of fluvial facies sand body was quantitatively characterized.