The fiber laser based on oscillating-amplifying integrated structure has the potential to take into account the advantages of fiber laser oscillator and amplifier with the characteristics of strong anti-back reflected light ability and high efficiency. Here, we achieved a 3.5 kW near single-mode (M²~1.24) oscillating-amplifying integrated fiber laser with an active fiber length of 8 m in the oscillating section and 17.6 m in the amplifying section. While operating at the maximum power, the optical-to-optical conversion efficiency is 87.0%, and the intensity of stimulated Raman scattering is about 23.61 dB lower than the signal light. As far as we know, this is the highest output power of the oscillating-amplifying integrated fiber laser, accompanied with the best beam quality and the highest efficiency.