Chinese Acad Sci, Inst Theoret Phys, Beijing 100080, Peoples R China
; Chinese Acad Sci, Grad Sch, Coll Phys Sci, Beijing 100049, Peoples R China
; Chinese Acad Sci, Inst High Energy Phys, Beijing 100039, Peoples R China
; CCAST, World Lab, Beijing 100080, Peoples R China
The w-w(') plane, defined by the equation of state parameter for the dark energy and its derivative with respect to the logarithm of the scale factor, is useful to the study of classifying the dynamical dark energy models. In this note, we examine the evolving behavior of the two-field quintom models with w crossing the w=-1 barrier in the w-w(') plane. We find that these models can be divided into two categories, type A quintom in which w changes from >-1 to <-1 and type B quintom in which w changes from <-1 to >-1 as the universe expands.