Tradition single cluster architecture has limit in expansibility, which is not so good when used in business tier of large-scale application.
In this paper we present multi clusters architecture, which can provide more strong expansibility. And we present a new method, named LBBCP (Load balance based on Business Component Partition) , to implement load balance across multi clusters. LBBCP makes formal description to the configuration of multi clusters and the properties of business components in the early stage of software lifetime, obtains business components partition schema by the way of mathematics, and implement load balance across multi clusters based on business components partition.