With the aim to reduce the effect of the figure of a dome on the imaging quality of optical system for a missile and to decrease the flying drags of the missile, the figure of the dome was investigated and the outside and inside figures of the dome were optimized. Firstly, the Calculated Fluid Dynamics(CFD) simulation and a wind tunnel experiment were compared to obtain the accuracy simulated parameters, and the normalized relation function between the ellipticity and the drag of dome was derived by the CFD simulation. Then, the Optical Path Difference(OPD) was used to evaluate the normalized relation of the optical performance and ellipticity, and the optimized outside figure could be obtained after determining the weights of the aerodynamic and imaging quality. The obtained outside figure is an elliptic with R=37.5 and C=-0.75. On the basis of the outside figure and by taking the minimum deviation of the light through the dome as an optimizing goal, the optimized function was established by using ray tracing method, and an optimized inside figure of the dome was also obtained. The inside figure is a conic with R=33.31 and C=-0.78. An analysis shows the optimized dome has excellent aerodynamics and good optical performances.