The amplification and nonlinear effects of 100 ps pulse in the diode-pumped Yb-doped double-clad fiber amplifier (YDDCFA) is investigated. The YDDCFA is seeded with 100 ps pulses with a spectrum centered at 1053 nm at repetition rate of 70 MHz and 1 Hz,respectively. The saturated gain of the quasi-continuous pulse input signal with average power of 55 mW,spectral width of 0.016 nm,is 7.02 dB. And the spectrum broadening caused by SPM is 0.01 nm,measured with F-P interferometer. The SRS is observed when the peak power of the single-shot pulse is amplified to 6950 W corresponding to a gain of 29.3 dB. Novel methods are devised to detect the spectrum of single shot. The change of spectrum caused by SPM and SRS is measured using a stretched fiber Bragg grating;and the Stocks pulse and signal pulse are separated using the dispersion of long sing mode fiber,revealing the SRS effect. Experimental results show that the SRS is the main limit of amplification of 100 ps pulse.