To buy authentic Cao Xian in Yangshengtang, it is recommended to buy it through official channels to ensure the authenticity and quality of the products. Yangshengtang official website or officially authorized e-commerce platforms, such as Tmall and JD.COM, are reliable purchase channels. Pay attention to the packaging, labels and anti-counterfeiting labels of products when purchasing, and ensure that they are consistent with the information provided by the government. Moreover, you can refer to the purchasing experience and evaluation of other consumers to understand the word-of-mouth and word-of-mouth of products.