Abstract: Reducing the execution time of program is a main goal of parallel processing ,while an efficient task allocation algorithm is a crucial step,especially on NOWs. A sub\|optimal algorithm OPTA on allocating a single task cluster to physical processors is presented in the paper here, and this task cluster is a common parallel paradigm in most parallel programming languages.An experiment of comparing with algorithm MH is made, and the results show that algorithm OPTA cuts 10% cost.