In computer network research, it is often necessary to build running network application environments using simulations to perform network verification and investigate theoretical or engineering problems. With the development, software defined networking (SDN) can be combined with Docker container technology to build lightweight virtual networks with centralized control and high fidelity. Virtual networks built using Docker containers require fewer physical resources compared with virtual machine-based approaches, particularly for simulating large-scale network scenarios. There is an urgent requirement for a user traffic injection tool for Docker containerized virtual networks to facilitate experiments and performance evaluations for large-scale network data planes. Therefore, this paper proposes combining Python and Docker technology to build a network user traffic injection tool, to realize large-scale user traffic injection and user defined traffic generation, and implement effective traffic injection for Docker based virtual networks.