Abstract: Conventional seismic data processing will be suppressing multiple waves as interference wave. Multiple waves are the feedback of reflected wave spread in the formation back and forth, so it carries information of reflection coefficient. Base on the causes of multiple waves, this article deduces reflection coefficient formula, that is the deconvolution of the first order multiple wave and the reflected wave. The theoretical model shows that the method is correct. The reflection coefficient is matched roughly with the reflected wave in processing of single channel seismic data. Because of the limitations of SNR, wavelet and deconcolution algorithm, this method needs further research.