Abstract: Navigability of the Arctic passage is highly affected by the complex sea ice conditions and the navigational risk level is different for ships of different ice classification notation. This situation suggests that special navigable window should be decided for particular type of ships. The POLARIS (Polar Operational Limit Assessment Risk Indexing System) proposed by IMO (International Maritime Organization) is studied. The RIO (Risk Index Outcome) for Ship Yongsheng's first voyage through the Arctic Northeast Passage is calculated based on the ship's ice classification notation and the ice condition data of the Arctic waters in 2011~2020. The navigational condition of each passage segment is studied and the navigable widow for the ship is decided. The calculation indicates that for the past decade the navigable period started on August 30 and ended on November 16, 79 days in average. The method here can be used by shipping companies in planning voyages for ships with different ice classification notations.