Abstract: In order to solve the problem of low accuracy of traditional non-equal interval gray model, firstly the optimal generating sequence of weight coefficient was introduced to the traditional non-equal interval grey model, and then Fourier transform function was used to correct the residual error, so a combined prediction model of weight optimization-Fourier transform function residual correction was formed. Then the deformation of the main beam of a through-type arch bridge with distributed arch-ribs was predicted. The prediction results showed that the overall average relative error of the prediction value was 2.4%, which was better than that of the traditional non-equal interval grey model, and the prediction accuracy was grade 1. The establishment and application of the new model provide an effective technical means for the deformation prediction of main beams.