The theoretical model of high-power fiber incoherent combined beams propagating in atmospheric turbulence is established, including single mode laser and multi-mode laser. The influences of collimating system, mechanical jitter and atmospheric turbulence are considered. The results show that the beam quality′s degeneration ratio of 10 kW single mode fiber laser is 10% resulting from the collimating system. And the ratio of 30 kW multi-mode fiber laser is 1%. For six incoherent combined beams without tip-tilt correction, the advantage in propagation performance of single mode beam decreases with the increase of the intensity of turbulence when the propagation distance is longer than 5 km. The maximum intensity gain due to tip-tilt correction of single mode beams is 1.32 times than without tip-tilt correction when the propagation distance is 5~15 km, while the gain of multi-mode beams is not obvious.