Embodiments of the present invention provide a system and a method for posture estimation, comprising: capturing a video sequence by a mobile terminal, the video sequence including a plurality of frames; extracting a plurality of convolutional features of a subject in the video sequence; estimating pose of a subject from the video sequence; constructing a model of the plurality of features from the estimated pose; estimating the posture of the subject from the plurality of features. The system also determines a key posture sequence from unconstrained video, where a mobile terminal captures a video sequence; a tracker estimates a reference subject; a posture estimator estimates a posture of the subject from plurality of features; a posture analytic unit assesses the estimated posture; a posture reconstructing unit reconstructs the posture into three dimensional space; an evaluating unit determines the estimated posture that should be added to key posture sequence.