Abstarct: Consumer psychology is one of the most popular trends of psychology in recent years which more than anything is related to understanding and analysis of consumer behavior. The most important fields of the science include issues such as expectations, preferences and customer loyalty. And scientists use statistical and quantitative tools to analyze customer behavior. this study in terms of objective is applied research, in terms of methodology is survey research and in terms of subject is marketing research. The purpose of this research is to measure the degree of customer loyalty to the product quality and product using Net Promoter Score (NPS) and Rough Set Theory (RST) instead of statistical methods and extracted rules and logical relationship between the calculated scales. For this purpose, data were collected from NPS questionnaire, is investigated through RST and Rosetta software. The proposed approach have been conducted as a case study on 250 samples from Sony Ericsson mobile phone users. The results show that Customers are dissatisfied with regard to the Aesthetic, Reliability and Durability dimensions, however, to creation positive halo effect on product desired quality dimensions, gives good sense to its user it leads to positive perception respect to that product.