Plantations provide important wood resources and also play an important role in mitigating climate change. Establishing poplar plantations is a common practice for improving the quality of reclaimed coastal saline soils in Eastern China. Organic fertilizer application and understory plant removal are two common management practices to promote plantation growth. Soil arthropod is a critical component in the ecosystem processes of organic matter decomposition and nutrient cycling. The abundance and diversity of arthropods can reflect changes in soil quality and ecosystem functionality. Studies have demonstrated that the abundance and diversity of soil arthropods might be impacted by changes in the quality and quantity of forest understory plant materials, as well as soil chemical and physical properties. However, the extent to which intensive forest management practices to alter soil arthropod communities remains elusive. In this study, we examined the effects of applying organic fertilizers (OF) and removing understory plants (UP), on the abundance and diversity (i.e. richness, evenness, and Shannon's index) of soil arthropods of poplar plantations in a reclaimed coastal area of northern Jiangsu Province, China. We found that Acari and Collembola were the two of the most abundant soil arthropod groups. The OF application significantly increased the total abundance of soil arthropod and the abundance of Acari, significantly decreased diversity index while UP removal decreased the total abundance of soil arthropod, the abundance of Collembola, evenness in 0-10 cm soil. Both of the two practices had no impact on the total abundance and diversity index at 10-20 cm soil. As a whole 0-20 cm depth of the soil, the application of the OF significantly increased the total abundance of soil arthropods, while it decreased the evenness and Shannon's index. The abundance of Prostigmata mites increased almost four folds with the application of the OF treatment in contrast to the control. The increased abundance of dominant groups led to the decrease in the arthropod evenness and Shannon's index based on the Order level. In addition, it was also presumably a consequence of reduced soil pH and improved soil properties (e.g., OM, TN, AP) with the application of the OF in this reclaimed coastal saline soil. The removal of understory plants did not significantly influence the abundance, richness, evenness and Shannon's index of soil arthropods in 0-20 cm depth of soil. Our results suggested that the organic fertilizers application is a preferable management practice to understory plant removal in order to elevate the abundance of soil arthropods while promoting poplar plantation productivity.