The status and effect of the optronic system in shipborne weaponry have been widely accepted, for which each developed country takes it as essential equipement in equipment developing programme. Following radar, shipborne optronic system is another important means of detection from single set to multi-set network system step by step. For reasons that shipborne IRST system can overcome four threats of radar and is an extremely effective short-range defense and countermeasure equipment for threat targets flying in low altitude and superlow altitude, so every navy has attached great importance to it. After transforming the operating range equation of an IRST system, the integrated efficiency coefficient Q is derived, by which factors of influencing the operating range of an IRST system and the approaches to improving the operating range and its feasibility are analyzed in the paper. In the present stage, because of limitations of D* the area of pixels and of an infrared detector, the major method for improving the operating range is to increase the aperture with the transmittance of an optical system remaining unchanged basically. However, increasing the aperture, remaining F number constant, increasing the focal length, reducing the effective FOV will decrease the spacial detective efficiency. So the integrated efficiency of an IRST system can be improved by optimizing the range, detective efficiency and so forth reasonably under existing conditions.