Using a two-layer model, Pedlosky had studied baroclinic insta-bility of zonal flow on a frictionless β-plane and on a f-plane withfriction respectively. On the basis of his findings, baroclinic insta-bility on a β-plane with friction and with heating from convectivecondensation is investigated, yielding linear results. A nonlineartheory will be discussed in a separate paper. The curves of critica1 shear (U_c^*)-wave number (A^*2) are used toanalyze the linear baroclinic instability influenced by β-effect, frictionand heating from convection. It is shown that not on1y the β-effectalone could contribute to increasing stability but its combination withfriction and heating from convection can also make the curves ofcritical stability asymmetrical. This implies that the positive andnegative shears of equal absolute values may differ in stability. Fric-tion (r) may serve as a stabilizing factor, but the β-effect with aweak friction is less stable than that without friction. Heating fromconvection (m^*) always increases the baroclinic instability and makesfriction a destabilizing factor when m^*> 1. Under the condition ofm^*< 1 and that dissipation exists in layers both above and below,the long-wave cutoff for A^*2= L^*2 appears in this model. And wavenumber of the short-wave cutoff increases infinitely as intensificationof heat (m^*→1) continues. In addition, medium-wave cutoffs also existin the critical curves.