Starting from 2-deoxy-D-ribose, ethanol/acetyl chloride was used instead of methanol/HCl to prepare 1-ethoxy-2-deoxyribose. And its 3,5-dihydroxyl group was protected by p-chlorobenzoyl chloride rather than p-methylbenzoyl chloride, taking dichloromethane as the solvent. Thus 1-Ethoxy-2-deoxy-3,5-di-p-chlorobenzoyloxy-D-ribofuran was obtained with 100% conversion rate. While the extra p-chlorobenzoyl chloride was removed by low-temperature crystallization. Followed by condensation of glycosides with 5’-azacytosine, deprotection by ammonia methanol, and isomer isolation, β-decitabine was synthesized. Structures of the products and intermediates were rigorously solved using 1HNMR, 13CNMR,MS(ESI), IR and X-ray diffraction. The yields of trial batch and kilogram-level scale-up batch were 30.61 % and 30.00 %, respectively.