The invention discloses a relay-free optical fiber transmission system, which comprises a transmitter, a receiver and a transmission link for connecting the transmitter and the receiver, and is characterized in that the transmitter comprises a laser, a first polarization beam splitter, an IQ modulator and a polarization beam combiner; the transmission link comprises an optical fiber, a first optical coupler, a second optical coupler, a forward Raman pump and a backward Raman pump; and the receiver comprises a second polarization beam splitter, a third optical coupler, a fourth optical coupler,a first photoelectric detector, a second photoelectric detector, a 90-degree polarization rotator, a 90-degree optical mixer, a first balance detector, a second balance detector and a signal processing module. The relay-free optical fiber transmission system disclosed by the invention is simple in structure and low in construction cost, but has good transmission performance, and can be applied tosome specific occasions. The invention also discloses a relay-free optical fiber transmission method.