This study presents a novel technique for the controllable preparation of photoluminescent substrates to enhance the photochemical microfluidic synthesis of vitamin D3.The dip-coating method to prepare the substrates was experimentally optimized,and the corresponding emission behaviors were systematically investigated.The substrates were successfully used to enhance the ultraviolet B (UVB) emission of a low-power light source (eg.,an 8 W lamp),whose UVB emission intensity was increased by approximately 11 times.By virtue of the novel light source,the productivity of a single set of photochemical micro reactor with a 12-meter-long channel (0.6 mm i.d.) was increased to 1.83 kg·a-1,which was 42％ higher than that of a 100 W lamp,and no cooling devices were used.The method is simple and has great potential to replace traditional medium-pressure mercury lamps for UVB-irradiated photochemical reactions.