4-Bromo-3-methylanisole is mainly used to synthesize black fluorane dye (2-anilino-3-methyl-6-dibutylaminofluorane, ODB-2), which is one of the most important heat and pressure-sensitive dyes in the manufacture of thermal papers. Compared to the industrial heterogeneous batch process, a continuous homogeneous bromination technology in a modular microreaction system has been developed, and 4-bromo-3-methylanisole has been successfully prepared through high-selective mono-bromination of 3-methylanisole with Br-2 solution in CHCl3. In optimal conditions, the content of bis-brominated byproducts can be controlled less than 0.5%, which is superior to the industrial standard with 99.5% 3-methylanisole conversion at very short residence time and mild reaction temperature. (C) 2020 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.