The invention discloses a preparation method of o-fluoroaniline, which relates to the field of organic synthesis, and specifically comprises the following steps: in a continuous reactor, the system is filled with water, and after three times of nitrogen replacement, the temperature is raised to 80°C, and the system is simultaneously pumped Put in o-fluoronitrobenzene, catalyst, inhibitory dehalogenation agent, water, (catalyst, inhibitory dehalogenation agent and water are mixed, stir evenly and pour in together) and hydrogen gas is introduced at the same time to ensure a pressure of 2.0MPa. Keep feeding continuously, the product is stratified through the stratified tank, and the product is obtained from the lower layer. Apply to the upper water layer. The preparation method disclosed by the invention is suitable for continuous large-scale production of o-fluoroaniline, has simple operation, high product purity and high yield, and the percentage content of the dehalogenated product is reduced to 0.02%.