Quantum Key Distribution (QKD) technology, based on quantum uncertainty principle, no-cloning theorem and Heisenberg uncertainty principle, can generate information-theoretically secure keys for communication parties. Typical QKD systems include the quantum communication phase and the post-processing phase and can be divided into three families: Device Dependent QKD, Source-Device Independent QKD and Measurement-Device Independent QKD. Nowadays, QKD is already mature enough for real-life applications. High-speed, long-distance and multi-access QKD technologies and security patches against quantum hacking are both continuously research tendency of QKD in the future.