The theoretical model in temperature field based on primary mirror of ground based telescope with the condition of non-linear ambient temperature and forced air flow upon the optical surface is analyzed. The analytical solution is gotten by separation of variables and Green function method. Take 4-m primary mirror as an example, the value of mirror seeing is caculated and anylised by using analytical solution of temperature field theory model. The effect of air flow upon the primany mirror seeing is discussed. The relationship between mirror seeing and air flow velocity upon the primary mirror is studied. Primary mirror seeing is analyzed with different ratios of mirror′s diameter to thickness. The temperature field of primary mirror of 4-m diameter is also studied by finite element method. The analytical solution is highly consistent with the solution of finite element method. The analytical solution of temperature field model has universal application value in designing telescope primary mirror.