Abstract: A finite element equivalent stress method for calculation of the stress in RCC high arch dams with different joint closure temperature fields is presented, focusing on the effect of these fields on dam body stress to improve the fields and determine reasonable arch sealing solutions. The results show that this effect is significant and a special study on joint closure temperature in design phase is needed. And the dam stress could be improved effectively through optimization of the temperature field by reducing the average temperature of the dam at its arch sealing stage and increasing its equivalent temperature difference at this stage. This work would provide reference for the design of joint closure temperature in RCC high arch dams.