The Quantum Simulation Teaching Software (referred to as the Qsim System) is a software designed for engineering education related to quantum key distribution. As a teaching system, the Qsim System can perfectly simulate the physical device setup and operation in offline quantum communication. Through self-directed learning of devices and experiments via the software, users can simply drag, connect, and configure parameters for offline implementation using the system's pre-built virtual device library, then run optical experiments to obtain experimental results.