In this paper, the time-stretch dispersive Fourier transform is applied to imaging femtosecond laser induced filaments. One-dimensional imaging of the transient evolution of a filament is realized by using spectral-spatial coding method combined with a fast photo-detector and an oscilloscope. The spatial resolution is 60 μm and the refresh rate reaches 54.54 MHz. The proposed method avoids the limitation of refresh rate caused by CCD and provides a new method for studying the dynamics of the filament-matter interaction.