Provided are a signal transmission method and apparatus. In the signal transmission method, a terminal device obtains a signal to be sent; and the terminal device sends the signal through a visible light medium, wherein after being demodulated, the signal sent through the visible light medium is carried on a power line for transmission. By virtue of the solution, the problem in related technologies regarding the integration of the visible light communication as a wireless access manner with the power line communication technology is solved, the construction of the communication network can be more convenient and faster, and the advantages of the visible light communication and the power line communication technology are fully utilized.