For the problem of information crosstalk that caused by periodic soliton string collision in the transmission,the modified symmetric split-step Fourier method that approximated by higher-precision Simpson algorithm was presented,and then the soliton string characteristics and transmitting procedure were simulated.It is impoint that the precision of method is more over than two orders of magnitude compared with the traditional method.The experimental results show that the solitons collision was decreased and the collision-free dependent transmission distance was increased,for the soliton pairs,three-soliton,four-soliton,five-soliton and six-soliton when only considered the self-steepening coefficient were 0.02 and only considered the self-frequency shift coefficient were 1,1,3,2 and 1.5,respectively.Meanwhile,the self-steepening and the self-frequency shift effect were simultaneously considered,the self-frequency shift effect was predominant effect.The results indicated that the suitable parameters have a significant influence for the amount of information of soliton transmission.