To research the performance of ground-based large telescopes and to optimize the design and structures of telescopes,the finite element analysis for the whole assembly was performed. For a 1.23 m telescope,the structural characteristics of main parts and their relation were studied,several kinds of simplification methods for some parts were discussed and a precise finite element model of the whole telescope assembly was established. Moreover,the gravity deformations of the telescope in both zenith and horizon pointing states were calculated and the deformation results of the primary mirror and the secondary mirror were given. Finally,the telescope assembly dynamic responses due to the wind loading and seismic excitation were analyzed. The obtained results show that wind loading will induce the optical axis misalignment of the primary mirror and secondary mirror, and the misalignment error RMS value is allowable in 0.025″. The displacements along three orthogonal directions induced by seismic excitation are greater, but the maximum stress is only 16.67 MPa, which cannot bring the damage to telescope structures.