It is widely used to compress pulse by using fiber loop mirror to eliminate pulse pedestal. The fiber loop mirror conventional consists of a dispersion decreasing fiber adopting 50∶50 (3 dB) coupler. In this paper,through the study of the fiber loop mirror composed of different pulse width and different types of dispersion decreasing fiber,it is found that the output pulse of higher compression quality can be obtained by using the non-uniform coupler of 60∶40 than that of 50∶50.