We have studied the classical theory of (e,2e) collision between electron and atoms or ions based on three kinds of one-dimensional models, i.e., the s-wave model, the collinear e-Ze- and Ze-e- models. We find numerically the relation of ionization cross sections with increasing energy obey different threshold laws, i.e., the linear law, Wannier law and square root law. These results have been also discussed analytically.