Mobile Internet is an integral part of daily life and the development of the world. The delay of mobile Internet directly affects the income of enterprises that provide Internet services and our living standards. According to research, DNS is one of the two most important factors affecting Internet latency. DNS relies on extensive caching for good performance. Additionally, each DNS zone provides caching to improve DNS response speed, but most caching is recursive. In terms of authoritative caching, except for the root cache, the caches of other tlds are less concerned. This paper analyzes the impact of domestically deployed .com and .net caches on resolution time, hoping to find out the impact of tld cache on DNS resolution speed. To this end, we have an online deployment at China Mobile Communications Group Henan Co., Ltd. A large number of experimental results show that the tld cache can greatly improve the DNS resolution speed and reduce the Internet delay.