Phosphatase plays an important role in microbial liberation of phosphorus in the soil systems. In this paper, the tundra ornithogenic soils were used to study the variations of the alkaline phosphatase activity (APA) with depths. Simultaneously, the organic carbon, total nitrogen, phosphorus, pH in the soils were also analyzed in these soils. The correlation between APA and soil chemical properties was discussed. In almost all soil profiles, the variations of APA showed the same patterns, the maximum appeared in the surface soils, and APA decreased with the soil depth. The APA ranged from 1.00 ppm to 1403.49 ppm with the average of about 408.31 ppm. APA showed a significant positive correlation with soil organic carbon (r=0.70, p<0.01) and nitrogen content (r=0.43, p<0.01), indicating that soil carbon and nitrogen contents were predominant factors affecting APA in polar soils. In addition, APA also positively correlated with inorganic phosphorus (r=0.40, p<0.05), organic phosphorus and total phosphorus（r=0.39, p<0.05）, suggesting that various forms of phosphorus, to some extent, affect APA in the soil systems. APA showed a significant negative correlation with Cu and Zn contents in the soils, indicating that Cu and Zn might inhibit APA in the polar soils. Our results showed that APA can be used as an important indicator of soil fertility in polar regions.