We demonstrate that large area eight-fold symmetric polymeric photonic quasi-crystals can be created by a specifically configured prism via single-exposure holographic lithography. The prism splits an expanded laser beam into five beams and in sequence converge onto a photoresist with a designed incident angle for forming an interference pattern with eight-fold quasi-period. Different from a conventional eight-fold symmetry prism, only five continuous surfaces are used. From group theory, we have verified the feasibility of the particular configuration. And numerical simulations have confirmed that the eight-fold symmetric periodicity can be obtained. Experimental results with the same five beam configuration are in good agreement with the theoretical prediction. The kind of specially designed prism may benefit mass production of large area photonic quasi-crystals by holographic lithography technique.