Abstract: Recently, Chou lifan put forward a principle about simplifying the full equations governing the motion of the atmosphere. This principle is used to discuss the properties of the Lorenz's low-order system. As a simplifying way, the low-order spectral method is satisfied with the principle. The quasigeostrophic baroclinic two basic kinds of the forms of waves and the orographic standing waves are two basic kinds of the froms of the large-scale atmospheric motions, they all have the characters of dissipative structures.