In the vertical breakwater reliability analysis, f, the friction coefficient of structure and the foundation bed, G, structure’s self weight, MG, the moment of stability induced by G, are often taken as constant values. But their impacts on the calculation results should not be ignored. Taking the breakwater in Qinhuangdao as an example, we verify the impact of structure’s weight and the friction coefficient taken as variables to the breakwater’s reliability. The JC method, mapping transformation method and Monte Carlo simulation method are used to calculate the reliability of the breakwater while f, G, MG are taken as constant value or variables. It is concluded that to take f, G, MG as variables is more reasonable. The variation of f makes little impact on the reliability calculation results, while the variation of G and MG makes much.