Java is one of the most popular programming architectures because of its platform-independence. Its platform-independence depends on Java virtual machine JVM. Compared to executing .class file on hardware JVM, executing .class file on software JVM is much slower. By studying we master the component architecture and the working principle of software JVM based on the .class file to explain the implementation process and to simulate the JVM. Currently, we are intended to design java chip. But, we should emulate the chip first. This paper gives the introduction of JVM and the interpretation principle which are necessary for emulator of java chip and gives the simulator design by software implementation and gives the result by an example.