In the troposphere, the higher the altitude ascends, the lower the temperature is. To compensate the influence of the change of temperature upon the image quality, an active-focusing aerial camera objective is designed, for which f is 400 mm, field of view 2ω is 10°, F number is 8, wavelength range is 460～750 nm, total track is 380 mm and back focal length BFL is 150 mm. This objective has perfect resolution, whose modulation transfer function fMT is no less than 0.52 at 70 lp/mm and the root mean square (RMS) diameter of the spot is 3.6 μm. A focusing group is equipped in this objective whose motion range is ±5 mm, and the 0.1 mm moving value is responsible for 0.026 mm in the image plane. The stationary thermal analysis and the temperature gradient emulation of the camera objective are presented subsequently. For the stationary thermal analysis, it is showed that after the active focusing, the aerial camera objective can obtain good image quality at the temperature range of -60 ℃～+60 ℃. For the temperature gradient emulation, each lens′ temperature gradient is set artificially which obtains the 20 ℃ axial and radial temperature gradients respectively; the result of the emulation shows that the objective can obtain good image quality at the 20 ℃ temperature gradient by active focusing.