Reflection grating pairs are usually used for femtosecond pulse compressing and stretching because of its advantage of negative dispersion. In this paper, a multi-level reflection grating based pulse compressor was presented, which is also called double-line-density gratings structure. It contains two four-step reflection gratings with periods of 40 μm and 20 μm, respectively, and the compressor has the efficiency of more than 70%. The input femtosecond pulses will go back along the input direction after diffractions of the two gratings, and in this way, the positive group velocity dispersion (GVD) of the input pulses is compensated. Using this compressor, the input pulses 66.8 fs are compressed into Fourier-transform-limited ones with the bandwidth of 46.6 fs. So it is demonstrated that, with high efficiency, low density reflective grating pair is an alternative approach different from prism pair as a compressor for both inside and outside femtosecond laser cavities.