In the upgrade process of enterprise information
systems, whether new systems will be success and their development
will be efficient, depends on how to deal with and utilize those legacy systems. We propose an evaluation system, which comprehensively
describes the capacity of legacy information systems in five aspects.
Then a practical legacy systems evaluation method is scripted. Base on
the evaluation result, we put forward 4 kinds of migration strategy: eliminated, maintenance, modification, encapsulating. The methods
and strategies play important roles in practice.