Together with other system software such as PVM, we use AVS as a candidate to integrate massively parallel processing modules(in data-parallel and/or explicit message- passing paradigms), sequential or parallel I/O, system control, visualization, data processing and other computing services required by a HPCC application, into a highly interactive, heterogeneous, high performance computing environment. We have demonstrated the use of AVS in two real-world applications, a stock option price modeling and an electromagnetic scattering simulation, and will further explore its system integration capabilities in on-going NPAC application projects, including geographical information system, four-dimensional data assimilation and environmental modeling.