The invention discloses a method for preparing organic isocyanate by using an injection circulation reactor, comprising the following steps of: preparing an injection circulation reactor, a gas-liquid separator and a stop device; dissolving organic primary amine in inertia organic solvent to prepare solution and introducing into an upper liquid-phase nozzle; introducing gaseous phosgene into an upper gas-phase nozzle; introducing the inertial organic solvent into a lower liquid-phase nozzle, and supplementing gaseous phosgene reaction through a lower gas-phase nozzle; introducing the reacted materials into the gas-liquid separator after leaving from a discharge hole; introducing the liquid phase stream obtained by separation in the stop device and reacting till the solution gets clear to obtain the organic isocyanate. By adopting the injection circulation reactor, the invention can improve the mixing efficiency between materials, reduce energy consumption for solvent recycling and phosgene recycling in the production of organic isocyanate, lower the production cost of the isocyanate and improve the production capacity of the isocyanate. The injection circulation reactor adopted in the invention has simple structure, reduces the danger for blockage of solid, is easy to seal and reduces the danger of phosgene leakage.