Inserting a metamaterial slab between the source and receiver coils of the wireless power transfer (WPT) system is a conventional way to improve the transmission performance. However, the free energy transfer space benefited from WPT system is impeded by the inserted metamaterial slab. This paper explores effects of side-positioned metamaterial slabs on wireless power transmission efficiency. Simulations of the WPT system indicate that the side-positioned metamaterial slab can achieve the same improvements as the center-positioned one in terms of the wireless power transmission, which was verified by experiments. In addition, the experiments show that more side-positioned metamaterial slabs can increase the transmitted energy significantly. Therefore the side-positioned metamaterial slabs are more efficient and flexible for enhancement of practical WPT systems.