The invention discloses a multi-wavelength single span transmission method. The method comprises steps that an optical signal is amplified by a first pre-amplifier, then enters a forward coupler and is output together with Raman pump light emitted by a forward associated Raman amplifier; an optical signal output from the forward coupler is transmitted to a first gain unit, second order pump light emitted by a simultaneous same direction bypass second order remote pump amplifier reaches the first gain unit and generates a gain, and the optical signal output by the forward coupler and also reaching the first gain unit is amplified; the optical signal output by the first gain unit is transmitted to a second gain unit, second order pump light emitted by a simultaneous reverse second order remote pump amplifier reaches the second gain unit and generates a gain, and the optical signal output by the first gain unit and also reaching the second gain unit is amplified; and the optical signal output by the second gain unit is transmitted to a dispersion compensating fiber and reaches a wavelength division system through the dispersion compensating fiber, then signal transmission is finished. The invention also discloses a multi-wavelength single span transmission system.