A 1 kW continuous all fiber laser is developed and introduced.Double end pumping and single resonance cavity are used.With the parameters of active fiber and fiber optical grating being optimized respectively,a continuous laser with a wavelength of 1.08 μm has been developed.The output power is 1.03 kW.The optical-optical conversion efficiency and slope efficiency are 74.6% and 75% respectively.When the output power is 272 W,M2x the and M2y are 1.39 and1.43 respectively.The cause that the beam quality is deteriorated is analyzed.Under high power,part of laser which is transmitted in the fiber core originally,leaks to the inner cladding from fiber optical grating,combiner and splicer.Then,the beam quality degrades by laser transmitting in the inner cladding.Improving approaches are introduced and discussed.