1. A method for performing mobile search utilizing a plurality of member engines, comprising: receiving a search request by a search server, wherein the search request carries: keyword information to be searched for, and an instant interest model of a user associated with the search request and a long-term interest model of the user which are acquired by a search application server, wherein: the instant interest model of the user is an instant interest model vector formed by score values of N dimensions, wherein: the score value of each of the N dimensions indicates an interest level of the user on said each of the N dimensions, and is calculated according to relevant data of a query sequence q(1),. .. , q(t-1), q(t) in a same search context session initiated by the user, wherein: the same search context session corresponds to the search request, and the search context session comprises a sum of a period of preset time before the current query q(t) occurs and a time when the current query q(t) occurs; calculating by the search server, a relevance score value of each member engine utilizing: the search request, meta index information describing stored contents of the member engine, the instant interest model of the user, and the long-term interest model of the user; and selecting by the search server, one or more member engines to search for the keyword information according to the relevance score value.