Internet computing and Grid technologies promise to change the way we tackle complex problems. They will enable large-scale aggregation and sharing of computational, data and other resources across institutional boundaries. And harnessing these new technologies effectively will transform scientific disciplines ranging from high-energy physics to the life sciences. In this paper, a grid computing environment is proposed and constructed on multiple PC clusters by using Globus Toolkit (GT) and SUN Grid Engine (SGE). The experimental results are also conducted by using the matrix multiplication to demonstrate the performance. On the other hand, the approaches to deal with scheduling and load balancing on multiple heterogeneous PC clusters computer system are not mature. Self-scheduling schemes which are suitable for parallel loops with independent iterations on heterogeneous cluster computer system have been designed in the past. However, these schemes, such as FSS, GSS and TSS, can not achieve load balancing in extremely heterogeneous environment. We propose a heuristic approach based upon a two-phase scheme to solve parallel regular loop scheduling problem on an extremely heterogeneous grid computing environment.