Based on Bayesian condition probability formula anc combined with convolution theorem, a theoretical formula is derived that utilizes output and response functions to acquire input function with deconvolution. According to the performance parameter in spectrograph and pointspread functions of main sources(theoretical formula of slit diffraction, grating diffraction and optical system aberration) the pointspread function of the spectrography is derived, and then this function is used to rectify the measuring result based on Bayesian deconvolution; using the difference of spectrum data before and after deconvolution, the concept “standard deviation of spectrum curve” is introduced to judge the data accuracy of the deconvolution output. The experimental result indicates that this method can effectively eliminate the influence of point spread function through iteration of system output, recover the original spectrum data from a “blurred” curve, and ultimately improve the accuracy of spectrograph.