In this paper we present a novel dynamic verification approach to protect the local host confidentiality from malicious Java mobile code. In our approach we use Bytecode Modification to add the verification function to the Java mobile code's class files before the local JVM executes them. Thus the verification work is done when the host JVM executes the modified class files. By this way our approach could achieve higher verification precision because the verification is done in runtime. Furthermore our approach can deal with the information flow in exception handling, which makes our approach more practicable.