We propose the two-stage cascaded-tapered silica photonic crystal fiber (PCF) for the supercontinuum (SC) generation. The cascaded-tapered silica PCF is designed to have a spatial periodic structure. The physical scenarios of the spectral broadening due to the interaction between the structure-induced periodic dispersion and Kerr nonlinearity under different pulse widths and peak powers are investigated. It is found that when the pump pulses with width of <100  fs and peak power of not more than 10 kW are propagated in the cascaded-tapered silica PCF, the SC with good coherence can be generated. It is believed that the research results have potential applications in the nonlinear photonics and spectroscopy.