A novel method is proposed to suppress the crosstalk of the DWDM system with dispersion compensated by fiber gratings, combining the merits of both concatenated narrowband fiber gratings and sampled fiber gratings. Random time delay is induced only between the adjacent channels to improve the characteristics of fiber gratings' linear crosstalk, with the cross modulation effects and the four wave mixing effects being suppressed simultaneously. Using this method，we can realize the low crosstalk multi-wavelength dispersion compensators based on fiber gratings.