A sodium–zinc sorbent based flue gas desulfurization technology (Na–Zn-FGD) was proposed based on the experiments and analyses of the thermal decomposition characteristics of CaSO 3 and ZnSO 3 ·2.5H 2 O, the waste products of calcium-based semi-dry and zinc-based flue gas desulfurization (Ca–SD-FGD and Zn–SD-FGD) technologies, respectively. It was found that ZnSO 3 ·2.5H 2 O first lost crystal H 2 O at 100°C and then decomposed into SO 2 and solid ZnO at 260°C in the air, while CaSO 3 is oxidized at 450°C before it decomposed in the air. The experimental results confirm that Zn–SD-FGD technology is good for SO 2 removal and recycling, but with problem in clogging and high operational cost. The proposed Na–Zn-FGD is clogging proof, and more cost-effective. In the new process, Na 2 CO 3 is used to generate Na 2 SO 3 for SO 2 absorption, and the intermediate product NaHSO 3 reacts with ZnO powders, producing ZnSO 3 ·2.5H 2 O precipitate and Na 2 SO 3 solution. The Na 2 SO 3 solution is clogging proof, which is re-used for SO 2 absorption. By thermal decomposition of ZnSO 3 ·2.5H 2 O, ZnO is re-generated and SO 2 with high purity is co-produced as well. The cycle consumes some amount of raw material Na 2 CO 3 and a small amount of ZnO only. The newly proposed FGD technology could be a substitute of the traditional semi-dry FGD technologies.