The effect of phase and amplitude fluctuation of lasers on the time-delayed laser-induced double gratings (TDLIDG) caused by thermal effect has been analysed theoretically in this paper. It is found that the modulation amplitude of four-wave mixing signal decays as the relative time delay between two pump beams increases. Experimental results agree quite well with the theoretical predication. We also demonstrated that, when TDLIDG was employed for the wavelength difference measurement, the accuracy could reach the same order of magnitude as the laser linewidth.