Performance-based salary system was introduced to national universities in 2011 without rational and valid performance evaluation system. In particular, the negative-sum property of performance-based salary was more strengthened by adding some of performance-based salary to the basic annual salary. We call it as the cumulative property of performance-based salary. This study uses life-time income model to find out institutional problems of the current salary system. They are summarized as follows. First, the cumulative property of performance-based salary is not appropriate as the incentive scheme for national university professors in that it makes life-time salary time-dependent. Second, the cumulative property of performance-based salary was more strengthened for retirement guaranteed professors because the base amount of performance-based salary increased with time. From the above findings, we conclude that the introduction of performance-based salary system should be deferred until the validity of performance evaluation is guaranteed.