The invention discloses a preparation method of nitrided iron nano-powder and a high-pressure gas-solid reaction bed of the nitrided iron nano-powder and effectively prepares the nitrided iron nano-powder in an energy-saving mode. The preparation method of the nitrided iron nano-powder comprises the following steps: ferric salt and alkali precipitator are quickly mixed in a reactor, and ferric hydroxide powder is obtained after the reaction; the ferric hydroxide powder is put into the high-pressure gas-solid reaction bed, and ammonia and gas storage tank gas are ventilated to conduct the reaction; under a sealing condition, reaction resultant is discharged into a material storage tank, and finally the required the crystal type nitrided iron nano-powder is obtained. The high-pressure gas-solid reaction bed of the nitrided iron nano-powder comprises a gas sparger, a powder supporting net, a heater, a quick connector, a material storage tank valve, a material storage tank, a heating power source, a thermocouple, a gas inlet valve, a gas inlet, a gas outlet valve, a gas outlet, a reaction bed side wall and a ventilation valve. The preparation method of the nitrided iron nano-powder and the high-pressure gas-solid reaction bed of the nitrided iron nano-powder are simple in operation and energy-saving, the rection equipment can be connected in parallel, and the batch production amount is big.