By using an ytterbium fiber laser with a repetition rate of 250 MHz and a pulse duration of 140 fs as the pump source, the expreiments of broadband supercontinuum generation were conducted with tapered Photonic Cystal Fibers (PCFs). After optimizing the waist diameter of the PCF tapers, when the pulse energy of the pump source is up to 0.36 nJ, a broadband spectrum was generated in the range from 470 nm to 1 620 nm at the level of －20 dB. After reaching up to 0.36 nJ, further increasing the pulse energy of the pump does not strongly benefit the spectral bandwidth in the visible range. The supercontinuum generation is verified by the simulation. In the simulation, the supercontinuum is generated in the input transition section, which is also observed in the experiments. By keeping the pulse energy of 0.36 nJ, this fiber survives with the high repetition rate pulses of 25 GHz, and obtains the －20 dB level spectral range from 450 nm to 700 nm in the visible range. A more than 12 h spectral evolution measurement shows the stability of the generated supercontinuum.