Soil salinization has progressed rapidly in northeastern and western China. In addition, air pollution is one of the most serious environmental problems. To alleviate the problems of soil salinization, food shortages, and air pollution, we have studied the amelioration of salt-affected soil using the by-products of flue gas desulfurization (FGD). Moreover, the recycling of waste gypsum produced at both new construction sites and demolition work sites has become a serious challenge in Japan. FGD gypsum in China and gypsum separated from waste gypsum board (WGB) in Japan were added to salt-affected soil as soil amendments. The effects of lignite and peat, which contains humic substances, were also investigated. With treatment, the soil's chemical parameters were restored, and agricultural production increased in all fields. Therefore, we have confirmed the effectiveness of amelioration of salt-affected soil by both FGD and WGB gypsum. Moreover, the use of lignite and peat with gypsum accelerated the effect of soil amelioration. This result suggests that the application rates of both types of gypsum could be reduced. Thus, we can propose a new salt-affected soil reclamation method using WGB, lignite, and peat in China.