To study the effects of buckwheat continuous cropping on grain yields, soil nutrients, and enzyme activities, a series of field experiments according to different continuous cropping years (2 years, 3 years and 4 years) of buckwheat without fertilization were conducted in the north semi-arid region. The results showed that with the increase of the buckwheat continuous cropping year, the buckwheat yield decreased, and significantly lower than that of CK which rotated with legume crops, and the contents of N, P, and K in rhizosphere soils decreased, particularly the contents of P and K, but soil pH increased. The enzyme activities of alkaline phosphatase (ALP) and catalase decreased, while that of urease decreased first and then elevated, that of sucrase decreased on the whole. In a word, to promote soil nutrients and achieve a high yield of buckwheat, it should rotate buckwheat with legume crops like kidney beans and apply fertilizers.