The objective of this research is to design a high-performance NAND flash memory system with a data buffer. The proposed buffer system in the NAND flash memory consists of two parts, i.e., a fully associative temporal buffer for temporal locality and a fully associative spatial buffer for spatial locality. We propose a new operating mechanism for reducing overhead of flash memory, that is, erase and write operations. According to our simulation results, the proposed buffer system can reduce the write and erase operations by about 73% and 79% for spec application respectively, compared with a fully associative buffer with two times more space. Futhermore, the average memory access time can improve by about 60% compared with other large buffer systems.