1. A recommendation system for search input, which comprises: a keyword acquisition unit, a search tree storage unit, a recommended word database, an address acquisition unit and a suggesting unit; the keyword acquisition unit is configured to obtain search keyword(s) according to a user input; the search tree storage unit is configured to store Chinese characters in a tree data structure, wherein each data node in the tree stores one Chinese character and address information of recommended word(s) containing the Chinese character; the recommended word database is configured to store the recommended word(s); the address acquisition unit is configured to query the search tree storage unit according to the search keyword(s) to obtain the address information of the recommended word(s); and the suggesting unit is configured to query the recommended word database according to the address information to acquire the recommended word(s) and then suggest the recommended word(s) to the user.