This paper measure the performance and load distribution among PC nodes in heterogeneous computer cluster system. the method used in this research is creasting a program to count the value of phiand modifying a module called MPI (message passing interface). the computer cluster system tested in this research consists of five pCs on local area network. in conclusion, the computer cluster reduce processing time significantly for high iteration workload (10,000,000 iterations) but it is not effective for low iteration workload (5,000 iterations). for high workload, the performance of 5 nodes cluster is 3.8 times faster than i node cluster. however, for low workload, the performance of 5 nodes is 0.12 time slower than 1 node cluster.