Cyclopropylamine (CPA) is an essential intermediate in the preparation of many biologically active substances. The traditional batch method to prepare CPA is facing many problems in the Hofmann rearrangement step, such as low production efficiency, poor stability, and complex process. In this paper, a novel continuous-flow method was developed to prepare CPA with high efficiency. Taking advantages of characteristics of the continuous-flow microreaction system, the simple process with a one-stage reaction was successfully realized instead of the original two-stage reaction in batch reactors. The yield of CPA reached up to 96% in only 4 min residence time at 90 degrees C. Interestingly, with the higher feed temperature, the reaction concentration in continuous-flow approach can be even higher than that in the batch method.