Product attributes are closely related to consumers' willingness to buy on e-commerce. Some products are considered that few people would buy them online, but in fact they have large sales volume, such as underwear products. This study analyzed from the perspective of the product grey private information of why consumers buy and who is buying these products, what kind of relationship between the purchasing comments and product attributes of these products. Firstly, we select the companies with certain influence to the exploratory research to study the company's comments, and do the data mining of the top 10 products of the best sales and the last 10 products of the poor sales. Secondly, we analyzed the product attributes of the 14 enterprises again by the iterative method and compared with the first exploration result. Thirdly, we studied on the value of common knowledge and outlier knowledge for these products. The study found that common knowledge has the sensitive interval for the price of grey private products, the product price, the discount of the product and the sales volume of the product have significant relationship. The discovery of outlier knowledge is open and the comfort is very different. There is a significant positive correlation between the time of marketing and the sales volume: simple, natural, health products and sales are related; the extreme situations are not universal, but have good room for growth.