The current IP address cache or IP prefix cache technologies have limitations. We analyse the overlapping relationships among prefixes in the global routing tables and propose a threshold-based routing cache method which combines IP address cache and prefix cache technologies without the need of prefix expansion. The threshold value K is selected according to the prefix overlapping features of global routing tables, which overcomes the shortcomings of address caching and prefix caching technologies. Comparison and simulation show that our scheme has better performance over other schemes in cache size, cache hit ratio, fairness among prefixes and incremental prefix updates. For a global routing table with more than 260 000 entries and cache size of 30 000, above 97% prefix nodes could be 1∶1 cached by prefix cache and the other prefix nodes could be cached by address cache with threshold K=4. Computation results show that high-speed forwording could be fulfilled with small cache size.