Abstract: Read rate is one of the bottleneck problems in the RFID food safety traceability system application. In this paper, the results of orthogonal tests were optimized gradually by using the rough sets theory. The optimal orthogonal tests gradually were conducted to investigate a low-cost optimal policy for read rate and the number of read tags in RFID food safety traceability system for the five factors which are the distance, deviation height, speed, number of rows and columns. All of those factors influence the read rate and the number of read tags of RFID system. According to the dependence degree of the Rough Sets theory, the greatest factor that influences the read rate most could be found, and the range of the level values of these factors could be searched emphatically, then iteratively the level value could be adjusted and the orthogonal tests were carried out, until the optimum orthogonal test level combination could be obtained by the approaching method. The study indicates that the method of the rough sets theory for optimizing the orthogonal tests gradually would be of benefit to obtain a higher RFID read rate and the much more numbers of read tags, and the optimum read rate is not less than 99.3% by the tested RFID food safety traceability system, which provides a powerful technical support for spreading the application of the RFID system in food safety traceability system.