Abstract: Anchoring security is very important to the icebreaker Xuelong during the voyages of polar expeditions. To analyze the feature of anchoring status, we built a decision tree model to recognize the anchoring pattern from the historical trajectory data from the 27th Chinese National Antarctic Research Expedition. On the basis of the recognition model, we retrieve the anchor position during the yawing period using the least squares principle. The fitting anchor position illustrates that the drag-anchor phenomenon occurred when Xuelong was in Antarctic Zhongshan anchorage on February 14, 2011. Combining with the meteorological data, we discuss the cause of drag-anchor and verify the feasibility of near-real-time anchor monitoring by using the fitting anchor position method.