By means of dual functional, we obtain the relationship between two different degree dual bases of Wang-Bézier generalized bases (abbr. WBGB). As the applications to WBGB dual bases, multiple degree reductions of WBGB curves with and without end-points continuities are given. Furthermore, it can be applied in offset approximation and other transformations in CAGD. Numerical examples and further discussions are also given.