In this paper, we present a new document classification based on physical layout features and graph b-coloring modeling. In order to reduce the computed time and to increase the performance of our automatic reading system, we propose to pre-classify the business documents by introducing an Automatic Recognition of Documents stage (ARD) as a pre-analysis phase. This phase guides the others involved in the recognition process of the documents contents. Once the document type identified, the reading system will use its corresponding information source to improve the recognition of its logical layout, the selection and parameterization of the OCR, and the final decision of sorting. The graph coloring model is introduced for both layout analysis and document classification. The proposed method is reliable, robust to various constraints and guarantees a real-time answer to the sorting ofbusiness documents.