Based on Ras Al Khair sea port berths No.5 & 6 project,we introduce the measures of mass concrete cracks control under the conditions of hot and dry extreme temperatures and marine environment for the breast wall designed and constructed according to the American standard.In the process of construction,by selecting the mixing ratio,materials’temperature control,pouring temperature control,hierarchical and segmental construction,maintenance and other comprehensive measures,we control effectively the crack of lmass concrete of the breast wall,and ensure the construction quality and progress.