The interaction between femtosecond optical pulses is studied by using numerical simulation. The results show that the interaction is different from that between picosecond optical pulses. Under the circumstance of nearer separation between solitons, the later is periodic repulsion and attraction, but the interaction of the former is more serious. At the initial moment, the interaction of femetosecone optical pulses is the same as that of picosecond optical pulse, but after the soliton pair become one pulse, they keep the state of repulsion and the separation between solitons increases along the distance. These can cause larger error code rate. The results also show that unequal amplitude method can reduce the interaction between femtosecond soliton in a certain degree.