The dialog manager is the most important component for a dialog system,in which the dialog state tracking is crucial to a real-world system.We claim that the intractability of dialog states comes from two aspects: the large slot size in users goal and the large candidate value size for each slot.For the first time,we propose a new focus strategy to deal with the former problem,by reducing the full slots of the users goal into a small subset focus slot.We also implement a partition-based method to deal with the latter problem.Then we combine both strategies to take advantage of their complement property.In our experiment of a real-world application in an image purchase domain,our proposed focus strategy is far faster than both the partition method and the na(i)ve algorithm with comparable quality.