The Java Card technology enables programs written in the Java programming language to run on smart cards and other resource-constrained devices. Smart cards represent one of the smallest platforms in use today. The memory configuration of a smart card is limited. The greatest challenge of Java Card technology design is to fit Java system software in smart card while conserving enough space for applications. The solution is to support a subset of the features of the Java language and to apply a split model to implement the Java virtual machine and to optimize Java bytecode. In this paper, we describe in detail the optimization algorithm of Java bytecode.