The main oscillation power amplification (MOPA) structure has become one of the mainstream designs of high-power fiber laser due to its good beam quality and adjustable parameters. In order to improve the output performance of high-power ytterbium-doped fiber laser (YDFL) and increase the optical-to-optical conversion efficiency of the system, a MOPA structure all-fiber high-power laser based on 915 nm pump laser and double clad ytterbium-doped fiber (YDF) was reported. The high-power fiber laser was composed of a seed laser pumped by an electrically modulated laser diode (LD) and a ytterbium-doped fiber amplifier (YDFA). In continuous wave (CW) mode, after the laser seed source passing through the YDFA, the laser output with the center wavelength of 1 069.96 nm was realized, and the maximum average output power was up to 945.9 W. The slope efficiency of the MOPA structure laser is as high as 74.12%, which has good robustness. The research scheme has reference significance for the development of high-power MOPA structure fiber laser.