中文摘要：

分析了基于IBM Model4的A^＊搜索算法和启发函数，由于仅靠启发函数难以找到最优译文，因此在搜索中采用了部分宽度搜索，以扩大搜索的范围。将该算法应用于汉英统计机器翻译中，实验结果表明改进后的算法获得了较好的翻译质量和效率。

英文摘要：

The A^＊ search algorithm and heuristic functions based on IBM Model 4 are described. As the search only depended on the heuristic functions is difficult to find the best translations, the partial breadth search to enlarge the search scope is added. The algorithm is applied to the Chinese-English machine translation. The experimental test result shows that the algorithm can improve translations quality and efficiency.