Abstract: With the rapid development of marine economy and increasing exploitation activities of marine resources, the role of the diving and salvage is prominent for the national emergency security system.In this context,the 4th Inter-national Symposium on Underwater Operations and Off-shore Industry was thus held by China Diving and Salvage Con-tractors Association(CDSA).The cutting edge research topics of the reports are summarized and discussed,which in-clude whole wreck salvage engineering,underwater operation equipment,intelligent ocean strategy,disaster relief and en-vironmental protection,as well as marine laws and regulations.With a brief review on developments and present status of the salvage system in China,perspective issues on key technologies and equipment developments,such as large-scale sal-vage ship,underwater high precision perception,deep diving,underwater robots,simulation rehearsal system,aided de-cision-making system,and underwater operation instruments are prospected.