The present application provides an optical port auto-negotiation method, including: a: selecting a downstream to-be-received wavelength; b: listening to a downstream message on the selected downstream to-be-received wavelength, performing c if a wavelength idle message is received, and returning to a if no wavelength idle message is received within a specified or fixed time, where the wavelength idle message is used to identify that the wavelength is not occupied or not allocated; c: sending a wavelength application message on an upstream wavelength, performing d if a wavelength grant message is received in a downstream direction; otherwise, going back to a or b, where the wavelength application message is used to identify a request for allocation of the wavelength, and the wavelength grant message is used to identify acknowledgment of wavelength allocation; and d: setting an optical port auto-negotiation success flag bit. The present application further provides an optical module.