Abstract: The helmet display being an important part of soldier digital equipments is always a hot spot in the field of high-tech military. The selection criterion for the design parameters of the projective helmet display is analyzed. The new 1.55cm OLED display was taken as the image source based on projection objective. The volume and weight of the optical system were reduced with the refractive/diffractive hybrid structure. The ultra-light and compact optical system for the 3-element helmet display was obtained by means of the system optimization with ZEMAX software. The weight of the optical system is only 1.35g and the diameter is 11.32mm. The resolution corresponding to the human eyes is 1.85 under the condition of the spatial frequency. The meridian and sagittal MTFs are all more than 0.2 at the wide FOV. The resolution meets the requirement of SVGA display mode.