Multisite resource selection and task scheduling is paid more and more attentions under the Grid environment nowadays with the emergence of high speed WAN. Especially in a distributed computational Grid, multisite resource selection and scheduling can significantly reduce the average execution time of grand applications with a limited demand in communication. Therefore we present a CGRS resource selection algorithm based on a new density-based grid resource-clustering algorithm, and implement it in our scalable environment. The analysis and experimental results show the correctness and effectiveness of our resource selection algorithm.