Based on the theory of quasi-phase-matched frequency doubling, the condition to generate the broadband second-harmonic is investigated. We analyze the conversion performances of the high efficiency broadband second-harmonic for type-0 (e+e→e) and type-Ⅰ(o+o→e) quasi-phase-matchad cases in periodically poled LiNbO3 crystal and 7mol% periodically poled MgO:LiNbO3 crystal. The results show that the central wavelengths of the fundamental wave and the bandwidth shift toward short waves in periodically poled MgO:LiNbO3 crystal, and the wider bandwidth is obtained in the type-0 quasi-phase-matched case.