An economically efficient one-step lactide synthesis process has been developed by using a low-price commercialized catalyst of SiO2/Al2O3 in a packed-bed reactor. Under the optimized conditions of preheater temperature 160 degrees C, reactor temperature 240 degrees C, and WHSV 3 h(-1), 90% lactic acid conversion and 99% lactide selectivity were obtained. Filling of glass beads underneath the catalyst bed proved to be quite effective in improving reaction performance. The catalyst stably maintained its activity for as long as 120 h showing no noticeable changes in its structure and chemical composition of the surface although a small amount of byproduct oligomers covered the surface. Oligomers deposited on the catalyst surface could be effectively removed by calcination at 600 degrees C.