The orientation effect for Below-Threshold Harmonics (BTHs) from H2+ was studied through the numerical simulations. With excluding the contributions of excited states successively, the orientation dependence of BTHs, obtained with the driving laser wavelength of 760 nm, was analyzed in detail. The research results show that the complex orientation dependence of BTHs parallel and perpendicular to the laser polarization is closely related to the resonance effect between the ground state and the neighboring excited states, where the axis symmetry of these excited states play an important role. A simple model which contains the transition dipole is used to explain these complex orientation-related phenomena. The main results are checked with using the first excited state as the initial evolution state. The results can give suggestions on relevant experimental studies of orientation dependence of BTHs.