A highly flexible quadtree structure has been introduced in the latest high efficient video coding (HEVC) to efficiently represent video content. However, the performance of the quadtre structure would be impaired when the video resolution is not an integral multiply of the largest coding unit (CU). To address this, a new CU splitting method on the frame boundary for arbitrary resolution video is proposed to improve the coding efficiency of HEVC. This method introduces the non-square CU to extend the CU candidate set on the frame boundary when the video resolution is not an integral multiple of the largest CU size. Simulation results show that the proposed method can reduce the coding bit rate by up to 0.76% compared with the original TMuC 0.9 reference software.