A high power self-similar fiber laser based on the Yb-doped large mode area photonic crystal fiber (LMAPCF) is studied by simulation and experiment. The laser is operated in an all-normal-dispersion region. To obtain higher power, the laser is performed by Yb-doped LMA-PCF without dispersion map with length of 1.9 m, which operates in the all normal dispersion. A ring cavity is employed and the stable mode-locking is achieved through nonlinear polarization rotation with a grating filter. The laser directly outputs the self-similar pulses with average power of 5 W at repetition rate of 72 MHz with pulse duration of 1.699 ps, corresponding to pulse energy of 69 nJ. The dechirped pulse is 84 fs which is compressed by a pair of 1200 line/mm transmission gratings. The laser shows good self-starting property with the beam quality factor M² of 1.41.