In this Letter, a novel, to the best of our knowledge, channel modeling scheme based on cascading chromatic dispersion-nonlinearity feature decoupling modules is proposed with the center-oriented long short-term memory (Co-LSTM) network structure adopted for modeling nonlinearity of each optical fiber span. By tracking the amplified spontaneous emission (ASE) noise at the output of each fiber span, the Co-LSTM-based channel modeling scheme achieves high waveform accuracy for long-haul coherent optical transmission compared with the conventional split-step Fourier transform method (SSFM) while saving calculation time by almost one order of magnitude.