In this work, a micromixing module was utilized in the polymerization of isobutylene (IB) initiated by tert-butyl chloride (t-BuCl) and catalyzed by ethylaluminum dichloride (EADC)/bis(2-chloroethyl)ether (CEE) complex for the synthesis of highly reactive polyisobutylene (HRPIB). Better micromixing performance resulted in HRPIB with narrower molecular weight distribution, where the PDI could be decreased from 3.5 without micromixing module to 2.5 or less. The polymerization rate also increased while the molecular weight and content of exo-olefin end groups of HRPIBs could be adjusted conveniently by the ratio of CEE to EADC and monomer concentration. A dynamic mechanism was proposed to explain the effects of micromixing on the enhanced HRPIB synthesis.