To keep pace with the fast growing computing power, the memory system of mobile devices has become more complicated and larger in capacity. As a result, the memory systems, especially the on-chip cache and the main memory, consume a major portion of the system energy. With the limited lifespan of the battery, the memory system of the mobile device demands energy-efficient design and techniques urgently. Without the exploration of the memory access patterns of the programs, it is impossible to fully exploit the potential energy benefits provided by the current memory hardware. This paper introduces the memory access patterns of the programs, describes its three main characteristics, and discusses how to develop energy-efficient techniques based on it in detail. In the end, some future trends in this area are discussed.