The invention discloses a routing table fast comparing method, which overcomes the problem that the efficiency of routing table fast comparison needs to be improved in the prior art. The routing table fast comparing method comprises the steps that: 1, routing tables are divided into a plurality of route subsets according to prefix lengths; 2, the route comparison process comprises a route subset prejudgment process and a routing table entry precise comparison process; 3, the route subset prejudgment process is implemented by means of a bloom filter of each routing subset; 4, the routing table entry precise comparison process is implemented by finding out a routing table entry having a route prefix the same as that of an table entry to be compared in the route subsets at first, and then compares the two entries according to a predefined judgment condition judging whether the two entries having the same prefixes are consistent; 5, the entries of the two routing tables participating in comparison are each marked with a ''consistent'' or ''inconsistent'' mark after the completion of the comparison. Through dividing the route subsets and introducing the Bloom filters for carrying out prejudgment, the routing table fast comparing method reduces the number of route comparison times in subsets.