Abstract: Credit allocation of each author of a multi-author paper has been a long standing concern. Regarding to the fact that the credit of each paper is not equal, this paper developes an improved credit allocation method, namely ACA_PR method. It uses the PageRank value and total citation of papers as total credit of one paper in order to measure the value of paper, and it constructs a co-citation network of collaborators’ scientific research records and cited research results, and distributes the contributions of the co-authors of the papers. By distinguishing the laureates of the Nobel Prize in Physics from the authors of prize-winning papers in American Physical Society (APS) dataset, this paper validates the ACA_PR method. Result shows that the ACA_PR method outperforms the state-of-the-art methods, and the accuracy of identifying the Nobel Prize laureates in Physics is 80.64% for 31 multi-author prize-winning papers in APS dataset. Accurate assessment the credit of researchers is significant in many aspects, such as hiring, funding and promotion, etc.