The rare earth-doped active fibers owning ten thousands of square-micron core-area but also delivering laser with high beam quality have little been reported. In this paper, we have designed a large-mode-area Yb<sup>3+</sup>-doped photonic crystal fiber in the cladding region with square-array air holes. Simulations demonstrate that only fundamental mode (FM) with mode-field-area (MFA) of ~15500 μm<sup>2</sup> can be amplified and propagated at the gain saturation, and the beam quality M<sup>2</sup> is less than 1.5. It is predicted that almost 58 mJ per-pulse can be available from such a 1.0 meter-length fiber, and the beam shape of amplified laser is near squared. It will be potential for so huge pulse-energy output from the VLMA LPF to be applied in the remote detecting, high-intensive welding and so on.