In the present study, the reliability design of semicircular breakwater is based on the verification of the rules defined by standard specifications, where partial coefficients are introduced to ensure safety. The reliability of the semicircular breakwaters has been analyzed by using the Hasofer-Lind method to determine the reliability index of structure that has correlated loads, utilizing the long-term observed wave data at a given place. The relation curve between reliability index and safety factor in the traditional design method, as well as the relationships between reliability index and partial coefficients, have been obtained. This paper proposes values of partial coefficients for the design expression of semicircular breakwaters in the cases of anti-sliding and anti-overtuming.