The invention discloses high-performance samarium-cobalt magnetic powder and a preparation method thereof. The general formula is as follows: Sm.alpha.Co. 1-alpha-gamma-delta-psi-omega.Fe.gamma.M.delta.Q.psi.R.omega., and the balance of Co wherein M is at least one of Cu or Zr; Q is at least one of Er, Gd, Dy or Ho; R is at least one of V, Cr, Mn, Sr, Al or Cs; alpha is greater than 20 wt percent and less than 28 wt percent; gamma is greater than 14 wt percent and less than 25 wt percent; delta is greater than 0.5 wt percent and less than 15 wt percent; psi is greater than 0.1 wt percent and less than 5 wt percent; and omega is greater than 0.1 wt percent and is less than 5 wt percent. Due to the composition, the consistency of columnar crystals growth can be promoted, so that the performances of the samarium-cobalt magnetic powder are improved; and the preparation method comprises the following steps of: compounding, smelting, pouring, sintering, solutioning, crushing, aging, adjusting granularity, and the like, so that the magnetic powder with the granularity in bimodal distribution can be prepared, the filler content of the magnetic powder is favored to be improved, and performances of the prepared samarium-cobalt magnetic powder are improved.