Abstract: Abstract: With the development of research and application of traceability systems, it plays a key role that the traceability system is established with appropriate granularity for deeper application according to the supply chain actual requirement and informatization level of subjects. The existing research in traceability width, depth, and accuracy were descriptive language, or lacked a quantitative evaluation model, which lead to the difference of the traceability system not being able to be measured well. In this paper, three layers of architecture of a basic traceability system were analyzed, which included product identification, information collection, and database construction of the center. The descriptive definition of traceability granularity was established with traceable unit size and its horizontal information capacity and longitudinal tracking depth. A two-layer index system was constructed with the core of traceability precision, width, and depth. The evaluation factors included a external traceability unit, an internal turning unit, an identification unit exchange, information collection content, information update frequency, forward tracing distance, and backward tracing distance. In order to eliminate qualitative indicators difficult to measure, a five point grading assignment method was used to obtain a qualitative index value. The evaluation factors' weight was confirmed using an AHP (analytic hierarchy process) method with three steps through investigation on 20 related areas experts. First, the initial judgment matrix and comparison matrix was established through the comparison of various elements. Secondly, a single order layer was taken. Finally, the final judgment matrix was obtained through the consistency test, and then all the target weights set were obtained. In the weights set, the external traceability unit weight was the highest with 0.1985. For the cooperative supply chain, an external traceability unit with the difference between a single product, single batch and the mixed batch, affected other unit sizes and information collection, so it played an important role in the whole index system. The lowest weight was an identification unit exchange with the value of 0.0872. Because the identification unit exchange had a correlation with an external traceability unit and an internal turning unit, the identification unit exchange had relatively less effects on traceability granularity with a determined internal and external unit. This research can provide quantitative evidence for evaluating the difference of traceability systems.