The invention belongs to the technical field of organic chemistry and particularly relates to a method for preparing a nitro compound from an aromatic hydrocarbon compound through isothermic tubular reaction. The method is characterized by comprising the following steps: adequately mixing two phases, namely a nitration raw material and mixed acid by virtue of a static mixer in a tubular reactor soas to realize simultaneous flow, reaction and heat exchange in a shell of the tubular reactor, and carrying out nitration separation, alkali washing, washing and refining, so as to obtain the nitro compound, wherein row tubes which can be controlled in different regions are arranged in the tubular reactor and are used for removing reaction heat. The method for preparing the nitro compound has thebeneficial effects that the flow is simple, the continuous production is realized, the reaction process is easy to control, the heat transfer efficiency is high, the situation that byproducts are increased due to the overheat in the reaction can be effectively avoided, the energy consumption and the raw material consumption are low, and the production process is safe and reliable.