A new flattening superfluorescent fiber source(SFS) with high power was obtained by using a fiber loop reflector made of 3 dB coupler,its linewidth is 35.28 nm with a power ripple of 3 dB without using any external spectral filters,and the output power is about 7.679 mW (about C-band),and the mean wavelength is 1 545.881 nm.A double-pass output was composed when a fiber loop reflector was added to the forward point of configuration.Compare with other methods,it is more simple,and easy to be realized,and it could enhance the efficiency of the pump LD and stability of the source,and has a lower cost,so the high flattening of C+L band with high power can be achieved easily.It is important for many applicant when high flattening and high power are needed at the same time.