A more general formula thinking over deconvolution coefficient for computing changes in the signal-to-noise ratio of the spectrum resulting from the Fourier self-deconvolution procedure was derived.Fourier self-deconvolution could reduce the intrinsic halfwidths of lines,which was in practice limited by the noise in the spectrum. The choice of deconvolution coefficient seriously influence the changes in the SNR of Fourier transform spectrum. With the help of the derived formula,the rate of decrease in the SNR as a function of apodization length for six different apodization function was studied,when deconvolution coefficient increased gradually. It was shown that when deconvolution coefficient increased gradually,the rate of decrease in the SNR become great rapidly.