The invention provides a target user determining method, device and system, relates to the field of communication technology, and solves the problem that a determined target user is relatively low in accuracy. The method comprises that an advertising request is received from a mobile advertisement platform, the advertising request comprises an advertising strategy and advertising demand information of an advertisement to be put, and the advertising demand information comprises key information of the advertisement to be put; the advertising strategy is determined to be a first strategy, a target data model corresponding to both the first strategy and the key information is utilized, the probability that each user in a pre-established user portrait library becomes a potential user of the advertisement to be put is calculated, and the pre-established user portrait library stores data, obtained by a server, of at least one user; and according to the calculated probability values, the server determines a target user of the advertisement to be put.