A two layer quasi geostrophic model forced by surface friction and radiative relaxation is used to study numerically the phenomenon of subcritical instability in baroclinic atmosphere.The numerical experiments show that when nondimension parameter β≥0.25,the phenomenon of subcritical instability can exist in two layer baroclinic atmosphere.The occurrence of subcritical instability is relative to the selection of the initial disturbances in model.The latitudinal gradient of Coriolis parameter is also an important factor that affects the strength of baroclinic stability,the larger its value is,the smaller strength of the baroclinic stability is.