This paper describes the dynamic load-balancing and high performance communication provided in Jcluster, an efficient Java parallel environment. For the efficient loadbalancing, we implement a task scheduler based on a Transitive Random Stealing algorithm, which improves the Random Stealing, a well-known load-balancing algorithm. The experiment results show that the scheduler performs efficiently, especially for a large-scale cluster. With the method of asynchronously multithreaded transmission, a high performance PVM-like and MPI-like message passing interface is implemented in pure Java. The evaluation of the communication performance is conducted among Jcluster, LAM-MPI and mpiJava on LAM-MPI based on the Java Grande Forum’s pingpong benchmark. Keywords. Dynamic load balancing, transitive random stealing, asynchronously multithreaded transmission, large-scale heterogenous cluster