<p>The primary reflector is the core component of the large-aperture millimeter wave sat-ellite antenna for observing solar flare, and its mechanics-thermology stability directly affects the working performance of the antenna. To make the antenna resistant to the harsh mechanical vibration environment during rocket launches and to keep the small surface error in the thermal environment of space, this thesis focuses on the objectives of ultra-lightweight, high stiffness, and minor surface error of the antenna. First, the material and ply angle used for the primary reflector are studied, and the scheme of M40 high modulus carbon fiber material and [0°/60°/−&#xa0;60°]₄ ply angle is selected by mechanics-thermology simulation and analysis comparison. Then, high stiffness is achieved by structural optimization of the primary reflector. Simulation results show that the first-order modal frequency of the antenna is about 119.94&#xa0;Hz, and the RMS value of the primary reflector surface error is less than 1/100 wavelength under extreme thermal environment. Finally, the vibration tests are designed to verify the simulation results. The test results show that most of the test data have the error of less than 10%, which proves that the modeling approach in this thesis is reasonable and the analysis results are accurate.</p>