A reasonable supporting structure between primary mirror and secondary mirror for a 1.2 m telescope was fabricated to meet its requirement for stiffness and the bandwidth of servo system. A four-vane spider effecting on the primary obstruction and secondary mirror stiffness was explored. The key parameters for the four-vane spider were selected by dynamic molding. Then, a finite element model was established in the ANSYS to perform static analysis and modal analysis. Finally, the modal analysis method was used to test the designed support structure. The finite element analysis shows that the designed structure effected by gravity induces about 0.004 2λ coma while the telescope points to the horizon, and the first-order modal frequency is about 57.2 Hz. The modal analysis indicates that the first-order resonance frequency is up to 54.1 Hz, which is in agreement with that of finite element analysis. Experimental results and FEA results are compared, and it shows that it is difficult to extract the modal when the vibration magnitude on the vane is smaller and obtained results are little smaller than that of the FEA, in which the maximum relative error is less than 7%. In conclusion, this design is not only a fewer obstruction but also an excellent stiffness, meeting the requirement of telescopes.