The influence of the double-clad fiber inner-cladding and core axial deviation on fiber splicing is theoretically analyzed. Based on the analysis of the results , in the master oscillator power amplifier laser system, a reasonable method to splice the key points is proposed. The 1509 W amplified power in all-fiber laser system at 1080 nm is achieved with a 533 W seed laser and a 1.16 kW pump power. The slope efficiency of the amplifier is up to 87.3% with central wavelength of 1080 nm, and the beam quality of the output laser is M2=1.46.