A method for determining an actual maximum gain of a Raman fiber amplifier, wherein a relationship between a maximum Raman gain and a 0km joint loss Att point[i] equivalent to a joint loss at different positions of one or more types of fibers, a relationship between a maximum Raman gain and a 0km joint loss Att coefficient[j] equivalent to a joint loss caused by a loss coefficient of the fibers, a relationship between a maximum Raman gain and a 0km joint loss Att Aeff[k] equivalent to a joint loss caused by a mode field diameter of the fibers, and a relationship between a maximum Raman gain and a fiber length are pre-configured, where i is a distance from a joint to a pump source, j is the loss coefficient of the fibers, and k is the mode field diameter of the fibers, the method comprises: obtaining (step 201) transmission performance parameters of a current optical fiber transmission line, the transmission performance parameters including a distance between the joint and the pump source, a fiber loss coefficient, and a fiber length; looking up (step 202-step 204) the relationship between the maximum Raman gain and the joint loss Att point[i], the relationship between the maximum Raman gain and the joint loss Att coefficient[j], and the relationship between the maximum Raman gain and the fiber length according to the distance between the joint and the pump source, the fiber loss coefficient, and the fiber length included in the transmission performance parameters to obtain a maximum gain impact factor A 1, a maximum gain impact factor A 2, and a maximum gain impact factor A 4, respectively; calculating (step 205) a 0km joint loss Att Aeff equivalent to a joint loss caused by the mode field diameter of the fiber in the current fiber transmission line according to the distance between the joint and the pump source and the fiber loss coefficient, and looking up the relationship between the maximum Raman gain and the joint loss Att point[k] according to the joint loss Att Aeff to obtain a maximum gain impact factor A 3; determining (step 206) the actual maximum gain G max_factual which the Raman fiber amplifier can actually achieve according to the impact factors A 1, A 2, A 3, and A 4. obtaining (step 201) transmission performance parameters of a current optical fiber transmission line, the transmission performance parameters including a distance between the joint and the pump source, a fiber loss coefficient, and a fiber length; looking up (step 202-step 204) the relationship between the maximum Raman gain and the joint loss Att point[i], the relationship between the maximum Raman gain and the joint loss Att coefficient[j], and the relationship between the maximum Raman gain and the fiber length according to the distance between the joint and the pump source, the fiber loss coefficient, and the fiber length included in the transmission performance parameters to obtain a maximum gain impact factor A 1, a maximum gain impact factor A 2, and a maximum gain impact factor A 4, respectively; calculating (step 205) a 0km joint loss Att Aeff equivalent to a joint loss caused by the mode field diameter of the fiber in the current fiber transmission line according to the distance between the joint and the pump source and the fiber loss coefficient, and looking up the relationship between the maximum Raman gain and the joint loss Att point[k] according to the joint loss Att Aeff to obtain a maximum gain impact factor A 3; determining (step 206) the actual maximum gain G max_factual which the Raman fiber amplifier can actually achieve according to the impact factors A 1, A 2, A 3, and A 4.