Abstract: To support the synchronization between the threads, the monitor enter and monitor exit bytecodes were deployed in a Java virtual machine, but this may introduce serious performance problems in many Java programs. Because the current software solutions may consume a lot of memory or lead to low performance, the picoJava core of Sun Microsystems supports the monitor operations in hardware. This technique can increase the monitor instructions’ performance significantly and reduce memory cost, but there is a high miss ratio when the monitors are entered. During the monitor operations in Java programs, the frequency of repeatedly entering a monitor is low but the monitor’s locality is obvious. Because of this characteristic, an effective support scheme in hardware and the corresponding operating algorithm are proposed in this paper, which can improve the hit ratio effectively and achieve a better performance.