We report a nanosecond-pulse amplification system based on an Yb-doped, 100-\mu m core, rod-type photonic crystal fiber. Up to 10W of average power with pulse energy of 1 mJ and peak power of 450 kWis obtained at the repetition rate of 10 kHz. The high-power nanosecond pulse has a good pulse shape and spectral characteristics. The usage of rod-type fibers provides a novel structure for nanosecond pulse amplification.