Nowadays Key-Value store system is widely used in various Internet services. However, the existing Key-Value store systems, mostly run in user-mode, can not meet the demands of high-concurrency and low-latency. It is mainly because user-mode usually provides inefficient access interfaces and transaction processing due to mode switch or context switch. To solve these problems, an in-kernel implementation of Key-Value store system, called KStore, was proposed in this paper. It had an in-kernel index and an in-kernel memory allocator, which were used to manage Key-Value data efficiently. To guarantee the low-latency response, KStore provided a remote interface based on in-kernel Socket, and a local interface based on file system. In addition, KStore processed concurrent requests with a novel mechanism based on in-kernel multi-thread. The experimental results show that KStore gains a remarkable advantage over Memcached in the characteristics of real-time and concurrency.