The Main Battle Tank (MBT) has a crucial war potential for any army. Thus, maintaining this potential at its maximum is a major concern of all countries. However, it is difficult to cope with the deterioration and obsolescence of MBTs throughout their long life cycle. These problems require well-organized system analyses and a system upgrade plan.This paper provides technical information on the improvement candidates and the strategies that must be considered in the upgrade plan of the Korean K-series MBTs. For the improvement candidates, 13 areas were identified and analyzed for the K1 series tank, and 17 areas for the K2 tank. For the implementation strategy, the recapitalization approach was recommended for the K1 series tank, and stepwise production of upgraded K2 tanks, following the pre-planned product improvement approach. For both approaches, it was recommended that an advanced long-term plan be prepared through collaboration among users and developers, which is currently non-existent.