China possesses long coastal line.China's vast area of marine territory is rich in mineral,petroleum and biological resources.To meet the demand of economic growth and energy security,we have initiated and built up an ocean petroleum industry system since 1970.Up to now,Chinese engineers are capable of designing and manufacturing jacket platforms in the coastal area as deep as 300 m.Recent pivot of the offshore oil industry and enterprises has shifted from shallow water region on the continental slope to the deep sea basin where the fixed platforms have to be substituted by compliant or floating structures.The most representative types of deep-sea structures are TLP,Semi-submarine,SPAR and FPSO.On the other hand,VLFS as an additional category especially designed for marine space utilization is regarded as a remedy of shortage in land.Obviously,it is considerably significant to restrict the motions of these structures within a certain range to guarantee normal drilling and production operations.