The invention discloses a method and a device for acquiring URL information. After communication link is established between a client and a site server, the method executes the following steps for each conversation between the client and the site server: third equipment analyzes a communication message transmitted to the site server by the client, extracts and records a URL linkage requested by the client; and the third equipment analyzes a communication message returned to the client by the site server, extracts and records link content information corresponding to the URL linkage according to a pre-supposed strategy. The invention also discloses switched routing equipment, mirror image equipment, a realizing method for a search engine and a system for the search engine. With the method,the acquisition of the URL information including information of a dynamic web page can be realized; moreover, the method replaces the prior technology of web crawlers, realizes the establishment of asearching database without occupying the bandwidth of the network. The searching database not only supports the searching to a dynamic webpage, but also improves the practicality and the effectiveness for the searching.