The effect of optical fiber dispersion parameter on the performance of average-soliton transmission system using PSA as in-line amplifiers has been analyzed theoretically by computer simulation. The simulation results show that because of the phase-sensitive nature of PSA′s gain, fiber dispersion will cause soliton pulse amplitude descending and its width broadening. Moreover it will result in pulse wings presenting. The larger the fiber dispersion is, the more significant the pulse amplitude descending and its width broadening are, as well as the higher the wing′s amplitude is and the wider its width is, after long distance transmission. So for this system, in order to realize long distance transmission, the optical fiber dispersion coefficient must be small.