The invention discloses an integrated micro-channel reaction device and a method for preparing 2-chloroethyl diphosphate diester by utilizing the reaction device. The integrated micro-channel reactiondevice is formed by connecting 5-9 stages of micro-channel reactors connected with one another in series, wherein the first stage is a preheating section, and the rest stages are rearrangement reaction sections; each stage of the micro-channel reactor comprises a plurality of annular pipelines; the annular pipelines comprise internal diameter pipes and external diameter pipes; the external diameter pipes are arranged at the peripheries of the internal diameter pipes in a sleeving manner; and the annular pipelines are annular spaces formed between the internal diameter pipes and external diameter pipes. With the adoption of an annular micro-channel, the integrated micro-channel reaction device disclosed by the invention has the characteristics of being thin in material layer, high in massand heat transfer efficiency, excellent in temperature stability, high in efficiency and low in energy consumption.