The application provides a method for measuring a dispersion coefficient of an optical fiber. A network device sends a first optical supervisory channel (OSC) measurement signal and a second OSC measurement signal, where wavelengths of the first OSC measurement signal and the second OSC measurement signal are different. The network device receives the returned first OSC measurement signal and second OSC measurement signal, where the first OSC measurement signal and the second OSC measurement signal are transmitted through a first optical fiber and a second optical fiber to return to the network device, and the first optical fiber and the second optical fiber are a to-be-tested optical fiber. The network device determines a delay difference between the received first OSC measurement signal and second OSC measurement signal. The network device determines a dispersion coefficient of the to-be-tested optical fiber based on the delay difference.