A tubular reactor comprises a tubular shell, an external jacket, and a gas distribution device at the top of the shell, wherein at least one group of feed nozzles are distributed uniformly on the shell, each group comprising at least one phosgene nozzle and at least one diamine nozzle; a reaction material is sprayed through the nozzles and impinges with each other in a middle impingement zone to strengthen the reaction effect, the gas distribution device is arranged at the top of the shell and the upper part of the feed nozzle, and an inert medium distributed uniformly through the gas distribution device is refracted at the top of the shell into an impingement reaction zone, so as to reduce the temperature and concentration of the reaction zone.