The embodiments of the present invention provide a nonlinear term selection apparatus and method, an identification system and a compensation system. The selection apparatus comprises: a linear coefficient calculator configured to measure linear properties of a nonlinear system by using measurement data, so as to obtain a plurality of linear coefficients; and a nonlinear term selector configured to select nonlinear model expanded terms of the nonlinear system by using the plurality of linear coefficients, so as to obtain nonlinear terms of the nonlinear system. With the embodiments of the present invention, the nonlinear model may be simplified, and the complexity of the nonlinear model may be lowered.