In this paper a single-channel chirped pulse amplification laser system based on Yb-doped photonic crystal fiber was constructed, which achieved a pulse energy output of 1 mJ with a beam quality close to the diffraction limit. Pulsed synchronous pumping was used to suppress amplified spontaneous emission at a repetition rate of 1 kHz. The de-chirped pulse width of 231 fs was achieved by precise systematic dispersion control, and the corresponding peak power reached 3.85 GW.