With the rapid improvement of modern computing applications, there is an increasing requirement of capacity, performance, and power consumption of memory system for both computingintensive and dataintensive applications. However, main memory based on traditional DRAM technology cannot fully satisfy the requirement because the improvement of DRAM technology is slower than that of CMOS technology. Moreover, it becomes even worse since the performance gap between HDD based storage and DRAM based main memory keeps increasing at the same time. Recently, the substantial progress of various nonvolatile memory technologies has provided an opportunity to mitigate this problem. This paper presents a survey of recent architecture and system level research work on nonvolatile main memory. It shows that different types of nonvolatile main memory can help improve performance and reduce power consumption of memory system significantly.