[Objective] The effects of freezing and thawing Cycles on nitrogen in fieldspathic sandstone and sand compound soil were examined in Yulin area of Northern Shaanxi Province, which was expected to improve soil fertility in Mu Us sandy land.[Methods] This paper studied the response of nitrogen mineralization processes in different mixed proportions of fieldspathic sandstone and sand compound soil to freezing and thawing by indoor culture experiment feature.[Results] The alternation of freezing and thawing had a signi-ficant effect on the mineralization of soil nitrogen, and the contents of nitrate nitrogen and ammonium nitrogen in three proportions of soils increased rapidly during the first cycle of freezing and thawing. After 2 cycles of freezing and thawing, the contents of nitrate and ammonium in compound soil decreased. In the period of 5 cycles of freezing and thawing, the contents of nitrate nitrogen and ammonium nitrogen in compound soil all began to show stable increasing trend. After 10 cycles of freezing and thawing, the contents of ammonium nitrogen in 1:1, 1:2 and 1:5 compound soil increased by 10%, 49% and 11% respectively, and the contents of nitrate nitrogen increased by 14%, 39% and 34%%. Especially, nitrate nitrogen and ammonium nitrogen contents the 1:2 compound soil were promoted significantly against the ones of 1:1, 1:5 compound soils, it performed better in nitrogen conservation.[Conclusion] Freezing and thawing cycles promoted the mineralization of soil organic nitrogen, which was beneficial to the accumulation of nitrate nitrogen and ammonium nitrogen in soil, which can provide sufficient nitrogen for the growth of crops in early spring.