Abstract: A centimeter-scale 3D microfluidic chip with high density and large liquid-holding capacity was fabricated using femtosecond laser micromachining technology, and sodium tanshinone IIA sulfonate was continuously synthesized within the microfluidic chip using sulfur trioxide as the sulfonation agent. The average residence time, factorless variance and various model parameters obtained from the residence time distribution test of the microfluidic chip at different flow rates showed that the actual residence time in the microfluidic chip was close to the theoretical residence time, the overall flow state in the microfluidic chip was close to the pushover flow, and it could effectively inhibit the occurrence of the side reaction in the local area caused by the back-mixing. We also determined that the greater the fluid flow rate, the more pronounced the effect flow. The effects of temperature, residence time and n(SO₃)/n(tanshinone IIA) on the yield of sodium tanshinone IIA sulfonate and the conversion of tanshinone IIA were investigated by one-way experimental analysis. The optimal process conditions were determined as follows: a sulfonation temperature of 25 ℃, n(SO₃)/n(tanshinone IIA) of 2.0, and residence time of 2 min. The products were analyzed by HPLC, indicating a yield of up to 92.3%, and a conversion rate of 97.2%. Comparing to the traditional batch process, the yield was increased by 35.7%, the ratio of sulfonating agent was reduced from 38 to 2, the reaction time was reduced from 120 min to 2 min, and the E-Factor reduced from 27.7 to 2.1. The generation of waste acid was reduced and production efficiency was improved. The green, safe, and efficient continuous preparation of sodium tanshinone IIA sulfonate was realized.