[Objective] To analyze the fluence of the freezing and thawing action and soil water content on soil available phosphorus in order to provide the basis for controlling agricultural non-point source pollution, confirming the phosphorus cycle process of soil in permafrost region, and assessing regional balance of the accurate phosphorus further.[Methods] Black soil in northeast China was sampled to quantify the effects of variable freeze-thaw cycles(FTCs), soil water(W) contents and contents of background available phosphorus (APb) on AP content. Soil samples were conducted to indoor simulated experiment with a maximum FTCs of 30 times and controlled temperature between -10 ℃ and 7 ℃. [Results] The effects of FTC decreased and no significant differences were found when FTCs fell between 20 and 30, while the APb content was the prominent factor during 5 to 20 and 20 to 30 cycles. During the whole 30 FTCs, soil AP content variation showed a characteristics of bimodal distribution. Meanwhile AP contents between adjacent FTCs showed significantly difference, the amount of which changed moderately with increase of FTCs changes in AP content were larger with a higher W content, and more stable with a higher APb content.[Conclusion] It showed that the impact of the three factors, FTC, W content and APb content, on AP content varied as the number of FTCs increased.