The paper analyzes the Four Wave Mixing(FWM) phenomenon of distributed raman fiber amplifier on Leaf.We observed the FWM phenomenon in broadband distributed Raman fiber amplifier(DRFA).This is one of the nonlinear effects which limits the performance of Raman amplified systems.We analyze the FWM effects for different fiber types.Finally we reduced the FWM influence successfully by choosing proper wavelengths in experiment.