According to the needs of upgrading,demolition and reconstruction of the gravity caisson wharf,the basic data such as the current status of caisson,the transportation path and distance,and the temporary storage site are collected,and the design of the caisson reuse scheme is carried out.Combined with the construction conditions of project example and the characteristics of LNG wharf with high design standards,six risk factors are extracted from the three major technical points of design,construction and economic,including wharf plane design,caisson detection and evaluation,caisson floating or removal risk,construction technology,engineering progress and engineering investment.By constructing the risk situation structure model,the risk factors are measured with clear quantitative indicators,which provides an important basis for recommending scheme 2,namely only the backfill material inside the caisson is used for the LNG wharf.The risk and investment of the scheme are controllable,and the construction progress is fast,which provides a stable working face for the subsequent construction of the new wharf on schedule.