The stiffness of titanium alloy panel of high speed vehicle will change in thermal environment, which will affect the modal characteristics of the vehicle. This paper first analyzes the modal and thermal buckling of stiffened titanium alloy panel with four sides simply supported at room temperature. On this basis, the influence of uniform thermal environment on the natural frequency, the contribution of material stiffness and additional geometric stiffness to the thermal stiffness of the stiffened panel and the "evolution" phenomenon of natural mode are studied. Finally, the influence of non-uniform thermal environment on thermal modal of the stiffened titanium alloy panel is studied. The results show that, the symmetry of numerical model under uniform temperature leads to the same second and third-order critical buckling temperature and natural frequency, and the "evolution" phenomenon of the second and third-order natural modes occurs under the influence of thermal environment. The first four-order natural frequencies of the stiffened panel show a trend of decreasing first and then increasing, and the minimum natural frequency is mainly affected by the first-order critical buckling temperature. Relative to the material stiffness, the additional geometric stiffness caused by thermal stress is the main factor for the thermal modal of the stiffened panel. Under uniform and non-uniform temperature field, the influence trend of thermal environment on natural frequency is the same. The non-uniform temperature field has little influence on the low order frequency, but has great influence on the high order natural frequency.