Continuous cropping of yam leads to a decrease in yield and soil elemental content，and different previous crops planting become an effective solution. However，the effects of different previous crops planting on soil medium and trace elements under yam cropping is not clear. In order to investigate the effect of different previous crops on the soil medium and trace elements under yam cropping，and to find more suitable previous crops for yam growth，the arable soils of three different previous crops(watermelon，cotton，yam)in the yam growing area of Wujiaqu city were taken as the research object to investigate the effects of different previous crops on the soil nutrients and available state of medium and trace elements(Fe，Mn，Zn，Cu，Ca，Mg). The results showed that:(1)Compared with cotton and yam as previous crops，soil pH significantly decreased by 0.75% and 2.38%，respectively，while organic matter and available potassium content significantly increased by 21.19%–24.77% and 23.62%–47.99%，respectively，when watermelon was used as previous crop.(2)When compared with yam as a previous crop，watermelon and cotton as previous crops significantly increased soil available magnesium content by 8.80% and 7.46%，respectively.(3)Different previous crops significantly affected soil trace element composite index of yam planting area，which was the lowest when yam was used as previous crop and the highest when watermelon was used as previous crop. The principal component composite score model found that the highest micronutrient scores were found in yam when the previous crop was watermelon. In conclusion，watermelon showed the highest increase in soil nutrients and available magnesium when it was the previous crop compared to cotton and yam；therefore，watermelon was more suitable as a previous crop for yam cultivation in the arid zone of Northwest China. The results of the study could provide basic data support in the selection of yam crops，scientific management of soil medium and trace nutrient fertilization and sustainable use of land resources during yam cultivation in the arid zone of Northwest China.