The invention belongs to the technical field of ferrous metallurgy and particularly relates to a method for supplying oxygen and injecting powder in electric arc furnace steelmaking, which can be used for solving the problems that the oxygen supply and jet attenuation speed is rapid in the current electric arc furnace steelmaking, the impact force is insufficient and the powder yield is low; the oxygen and powder particles are mixed into a gas-solid mixed phase to generate a high-speed mixed jet flow; the kinetic energy of powder particles is utilized to improve the impact force of the electric-arc furnace oxygen supply jet flow; stirring in the molten pool is strengthened; and the efficient transportation of the powder particles is realized. The powder flow range is 5-60kg/min, the oxygen flow is 500-3500Nm3/h, gas-solid mixed phase flow is 500-4000Nm3/h, the gas-solid ratio is 0.5-5kg/kg; and the high-speed mixed jet flow velocity is 50-700m/s. The method is suitable for 5-300t of electric-arc furnace steelmaking of wall furnace oxygen supply and powder injection; the stirring strength in the electric-arc furnace molten pool is strengthened by over 20%; the utilization rate of the oxygen and power is improved; the oxygen consumption is lowered to be larger than 15%; and the blowing powder consumption is lowered to be larger than 30%.