Abstract: On the basis of the transmission system model given in this paper, the impact of the parameters, such as input power, dispersion compensation coefficient, dispersion compensation factor, length of standard single mode fiber and pulse duty cycle on the system performance, which is evaluated by bit error rate and Q value of the system, is studied through extensive numerical simulation. Then a 9-span optical fiber transmission system with optimal parameters is designed.The simulation results are helpful to design systems based on bit rate of 40Gb/s or above.