In a conformal optical system, the incident parallel light rays are no longer parallel when transmitting through an ellipsoidal dome, and transform into diverging light rays which greatly increase the system′s aberration. This is bad for the subsequent aberration correction. This paper breaks the condition of equal thickness and redesigns the inner surface of the conformal dome. Consequently, the aberrations of system are corrected by using less optical lenses when compared with equal thickness dome. By analyzing aberration correction results of different order aspheric surfaces as the inner surface of dome, six-order aspheric surface is selected as the initial structure. By optimizing the inner surface of dome, the final shape of inner surface is achieved. The results show that this method obviously reduces the aberrations induced by the conformal domes. Finally, aberrations of the conformal dome are corrected by using the fixed correctors. The results show that the number of the optical elements decreases by redesigning the inner surface of the dome, and this method has a good effect on correcting aberrations.