A nonlinear compensating apparatus, comprising: an information acquiring unit to acquire a symbol information sequence of the pulse signal with a modulation format; a perturbation quantity calculating unit (202, 402) to calculate a weighted sum of several pulse interaction items at several different instants relative to a sampling instant, to obtain the perturbation quantity produced by the nonlinear effect at the sampling instant on a transmission link with certain length, wherein the perturbation quantity calculating unit (202, 402) comprises: a first information acquiring unit to acquire the symbol information of the pulses at several different instants relative to the sampling instant; a first calculating unit to calculate the weighted values of the pulse interaction items by using said symbol information of the pulses at several different instants relative to the sampling instant and pre-obtained weighting coefficient, and calculating the weighted sum of the pulse interaction items based on said weighted value of each pulse interaction item; a second calculating unit to calculate the product between the sum of the pulse interaction items obtained by the first calculating unit and a first preset value, to obtain the perturbation quantity produced by the nonlinear effect at the sampling instant on the transmission link with said certain length, the first preset value being related to the signal power and the nonlinear coefficient of the transmission link; the apparatus further comprising an information compensating unit to calculate the difference between the symbol information sequence acquired by the information acquiring unit and the perturbation quantity obtained by the perturbation quantity calculating unit, so as to obtain the symbol information sequence compensated at the sampling instant to cause a transmitting side to transmit signals according to the compensated symbol information sequence. an information acquiring unit to acquire a symbol information sequence of the pulse signal with a modulation format; a perturbation quantity calculating unit (202, 402) to calculate a weighted sum of several pulse interaction items at several different instants relative to a sampling instant, to obtain the perturbation quantity produced by the nonlinear effect at the sampling instant on a transmission link with certain length, wherein the perturbation quantity calculating unit (202, 402) comprises: a first information acquiring unit to acquire the symbol information of the pulses at several different instants relative to the sampling instant; a first calculating unit to calculate the weighted values of the pulse interaction items by using said symbol information of the pulses at several different instants relative to the sampling instant and pre-obtained weighting coefficient, and calculating the weighted sum of the pulse interaction items based on said weighted value of each pulse interaction item; a second calculating unit to calculate the product between the sum of the pulse interaction items obtained by the first calculating unit and a first preset value, to obtain the perturbation quantity produced by the nonlinear effect at the sampling instant on the transmission link with said certain length, the first preset value being related to the signal power and the nonlinear coefficient of the transmission link; the apparatus further comprising an information compensating unit to calculate the difference between the symbol information sequence acquired by the information acquiring unit and the perturbation quantity obtained by the perturbation quantity calculating unit, so as to obtain the symbol information sequence compensated at the sampling instant to cause a transmitting side to transmit signals according to the compensated symbol information sequence. a first information acquiring unit to acquire the symbol information of the pulses at several different instants relative to the sampling instant; a first calculating unit to calculate the weighted values of the pulse interaction items by using said symbol information of the pulses at several different instants relative to the sampling instant and pre-obtained weighting coefficient, and calculating the weighted sum of the pulse interaction items based on said weighted value of each pulse interaction item; a second calculating unit to calculate the product between the sum of the pulse interaction items obtained by the first calculating unit and a first preset value, to obtain the perturbation quantity produced by the nonlinear effect at the sampling instant on the transmission link with said certain length, the first preset value being related to the signal power and the nonlinear coefficient of the transmission link; the apparatus further comprising an information compensating unit to calculate the difference between the symbol information sequence acquired by the information acquiring unit and the perturbation quantity obtained by the perturbation quantity calculating unit, so as to obtain the symbol information sequence compensated at the sampling instant to cause a transmitting side to transmit signals according to the compensated symbol information sequence.