The Tertiary reefs in the Pearl River Mouth Basin have huge oil potential. Though the identification of reef's seismic feature and the analysis of sequence stratigraphy have achieved in progress, the analysis with system tract asa unit on sequence stratigraphy of reef reservoirs is seldom done. By analyzing the growth patterns of reefs in response to the sea-level changes, we have summed up several possible geometric patterns and the corresponding seismic feature for the growth of reefs in Dongsha Uplift in the Pearl River Mouth Basin at different times. In accordance with the foregoing understanding of the reefs, the geological interpretation on seismic reflection characteristics is finished anda model of reef formation is built to be aware of stratigraphic sequence of reefs with system tract as a unit. It can provide a more reliable reference to horizon contrast and the division of sequence boundaries.