The invention discloses a chlorinated butyl rubber synthesizing process and belongs to the technical field of chemical synthesis. The chlorinated butyl rubber synthesizing process includes two series processes, namely butyl rubber chlorination and neutralization of chlorinated mixed liquid. The process utilizes a pipeline type reactor to enable a C12 alkane solution and a butyl rubber alkane solution to be mixed and perform the chlorination, then utilizes the other pipeline type reactor and introduces alkali liquor into the reactor to start neutralization reaction after the solution stays for 6-60 seconds in a follow-up pipeline, and finishes the reaction after reaction solution stays for 20-300 seconds in the follow-up pipeline. The process has the advantages that the reaction speed is quick, the reaction time is short and can be accurately controlled, the conversion from a main product replaced by meso-position chlorine to a by-product replaced by primary-position chlorine is inhibited, and indexes of an obtained product are excellent.