The probability models of 2 different quantum cellular automaton (QCA) adders are based on the theory of probabilistic transfer matrix and circuit partition. The effect of individual component on the overall fault-tolerance is fully analyzed at the same level. The simulation shows that the effect of the wire is minor when the success probability is low, while the overall fault-tolerance rises sharply once the success probability is high. And the inverter is considered to be a major factor that affects the overall fault-tolerance in the variation range of parameter. Frobenbius norm of the overall error probabilistic transfer matrix is employed to study the fault-tolerance difference. The result shows that the overall fault-tolerance of QCA adder consisting of 5-input majority is superior to the other. Such fault-tolerance analyses should be used for a better characterization of QCA circuit design and fault-tolerance improvement.