The emergence of non-volatile memory (NVM) has introduced new opportunities for performance optimizations in existing storage systems.To better utilize its byte-addressability and near-DRAM performance,NVM can be attached on the memory bus and accessed via load/store memory instructions rather than the conventional block interface.In this scenario,a cache line (usually 64 bytes) becomes the data transfer unit be-tween volatile and non-volatile devices.However,the failure-atomicity of write on NVM is the memory bit width (usually 8 bytes).This mismatch between the data transfer unit and the atomicity unit may introduce write amplification and compro-mise data consistency of node-based data structures such as B+-trees.In this paper,we propose WOBTree,a Write-Optimized B+-Tree for NVM to address the mismatch problem without expensive logging.WOBTree minimizes the update granular-ity from a tree node to a much smaller subnode and carefully arranges the write operations in it to ensure crash consistency and reduce write amplification.Experimental results show that compared with previous persistent B+-tree solutions,WOB-Tree reduces the write amplification by up to 86× and im-proves write performance by up to 61× while maintaining sim-ilar search performance.