Four focusing models for generation of freak waves are presented. An extreme wave focusing model is presented on the basis of the enhanced High-Order Spectral (HOS) method and the importance of the nonlinear wave-wave interaction is evaluated by comparison of the calculated results with experimental and theoretical data. Based on the modification of the Longuet-Higgins model, four wave models for generation of freak waves (a. Extreme wave model + random wave model; b. Extreme wave model + regular wave model; c. Phase interval modulation wave focusing model; d. Number modulation wave focusing model with the same phase) are proposed. By use of different energy distribution techniques in the four models, freak wave events are obtained with different H_(max)/H_s in finite space and time.