According to the theory of sequence stratigraphy, using analysis methods such as seismic facies, seismic sedimentology and combining the drilling and logging datas, a study is conducted to the sedimentary evolution of the north slope of Baiyun Pearl River Mouth Basin . Results show that（1） LST of SQ21 mainly develops the shelf edge deltaic deposit;delta front deposit which is diamond in plane is distributed in PY35 well field and the southern and develops a large number of proximal dams and crevasse splay sand bodies;predelta is located in the southern region and develops plenty of fan-shaped turbidite inside(2) sedimentary evolution is controlled by sea-level fluctuation and provenance supply;the sudden change of sedimentary environment during the same period is caused by sedimentary slope break;(3)the frontal proximal sandbar ,distal sandbar and turbidite fan of delta in LST of low system fields of SQ21 are main lithologic and stratigraphic traps goal ;the northwestern edge of basin in transgressive system has beach bar sand body trap.