1. A method for searching target clients, applied to a mobile device coupled to a network, comprising: inputting at least one keyword; generating a target position by a positioning unit of the mobile device; generating a target time by a time generating unit of the mobile device; generating a target clients search message according to the at least one keyword, the target position and the target time, and transmitting the target clients search message to a server coupled to the network through the network; receiving a search result transmitted by the server through the network, wherein the search result comprises at least one of a target clients amount, a target clients density and a target clients occurrence probability, which are retrieved from at least one social networks data and corresponding to the at least one keyword, the target position and the target time; displaying a map combined with the search result; retrieving, by the server, a plurality of potential clients corresponding to a location range and a time range from the at least one social networks data according to the location range and the time range and counting an amount of the plurality of potential clients to obtain a potential clients amount, wherein the target position is included in the location range and the target time is included in the time range; comparing, by the server, data corresponding to the plurality of potential clients in the at least one social networks data with the at least one keyword, retrieving a plurality of target clients corresponding to the at least one keyword and calculating an amount of the retrieved target clients to obtain the target clients amount; calculating, by the server, the target clients density according to the target clients amount and the potential clients amount; calculating, by the server, the target clients occurrence probability according to data corresponding to the plurality of target clients in the at least one social networks data, the time range and the location range; and providing the target clients, the calculated target clients density and the calculated target clients occurrence probability.