A computational investigation has been adopted for design an optical system for infrared (IR) homing head, operated in region of spectrum (3-5) µm. The characteristics of the present optical system design include the modulation transfer function (MTF) and spot size. These characteristics are determined which give the efficiency and accuracy of the design optical system. Our work has been performed in two stages namely; design and improvement, to get the efficiency of the developed optical system. The design stage depends originally on a standard optical system for IR homing head. Some modifications and improvements have been imposed on the standard design to achieve a new one of high quality characteristics. These improvements include choosing the most suitable materials and features for each optical element in the developed design. An improvement stage was then followed on the radius of curvature of correcting lens, which has process carried out by Zemax software to determine the most favorable optical properties i.e. spherical aberration, size of spot, and size and shape of the system. It is appears from all results that the best suggested suitable materials for IR homing head is Sapphire when use in manufacture dome and correcting lens. Also, the Germanium materials can not be used in manufacture the dome.