The government enacted the Defense Industry Technology Protection Act in 2015 to prevent the outflow of defense industry technology. As a result, defense companies are subject to two similar security policies, which reduce the efficiency of their security operations, including increased security administration needs and wasted budgets. Against this backdrop, this study drew preliminary assessment indicators by comparing and analyzing the defense industry security management system, information protection management system and industrial technology protection guidelines, and developed the defense industry security level assessment index using Delphi technique and AHP technique. The 「Defense Industry Security Level Evaluation Index」 was developed into 8 major categories, 37 middle categories, and 139 evaluation items divided into unique items(2) and common items(6), and the characteristics of the evaluation index are as follows. The priorities for the evaluation items in the major categories (8) and middle categories(37) were presented so that the security level can be efficiently diagnosed and the security system can be systematically established. This study is the first ‘Defense Industry Security Level Assessment Index’ developed by analyzing the entire defense industry security management system, and can be used as basic data for various studies such as development of defense industry security policy in the future.