In the course of digital library's construction and development, both service categories and resources storages are increased. We should consider the problem of how to purchase device and deploy application reasonable, how to provide stable, flexible and fast services to the users. We get the experiences of using load balances to solving this kind of problem during we upgrade the EI server. In the first part of this paper, the category and strategy of load balance are exposed, and in the second part of this paper, the load balance's application instance of EI server is expanded.