In an ongoing project at NHPCC (National High Performance Computing Center) at Hefei of China, we are building a debugger for parallel/distributed programs that run on a cluster of homogeneous workstations-Dawning cluster system. Such debuggers are commonly built by layering a sophisticated user interface on top of existing sequential debuggers, such as dbx or gdb. We employ object-oriented technology in our work by using Java as the programming language. This paper describes how we design and implement the debugger DCDB, the problems encountered and their solutions.