The engineering quality control of mass concrete structure is difficult. During the construction of Sanya Phoenix Island International Cruise Port phase II project，in order to ensure that the mass concrete structure quality meets the design requirements，before the formal construction of mass concrete，the production，pouring and curing of mass concrete test blocks are carried out by simulating the on-site working conditions，and the internal temperature and strain change laws of mass concrete test blocks are monitored. The optimization of concrete mix proportion design is studied. A better concrete mix proportion is obtained through two groups of comparative tests of different concrete mix proportions（water binder ratios are 0.38 and 0.40 respectively）under the same conditions. The results show that the maximum temperature，maximum temperature rise，internal and external temperature difference and maximum cooling rate of concrete block with water binder ratio of 0.38 are higher than those of concrete block with water binder ratio of 0.40. It is recommended to select water binder ratio of 0.40 for mass concrete construction in high temperature areas.