Using phase-sensitive amplifiers (PSA) as in-line amplifiers to suppress soliton interaction in soliton transmission system was theoretically analyzed by computer simulation. For comparison, the interaction of soliton in the system using erbium-doped fiber amplifiers (EDFA) as in-line amplifiers was also simulated. The simulation considered both average-soliton regime and dynamic-soliton regime. The results show that using PSAs instead of EDFAs as in-line amplifiers can effectively suppress the pulse broadening and soliton interaction. For average-soliton, without additional control techniques, the interaction between solitons can be suppressed and the steady transmission distance can be lengthened greatly. For dynamic-soliton system, PSA also has a good behavior of suppressing soliton interaction. But after long distance transmission, the amplitude of soliton pulse descends significantly.