Baidu has many SEO keyword optimization methods, including determining core keywords, long tail theory and long tail keywords, keyword expansion tools and so on. Among them, the methods to determine the core keywords are brainstorming, investigating colleagues, friends, users, checking competitors' keywords and search times. The characteristics of long-tail keywords include wide range, large coverage, long tail effect and strong correlation with website content or main keywords (target keywords). The most common tools for keyword expansion are Baidu backstage (baidu promotion) keyword tool (keyword planner), and the drop-down menus of search engines and related searches, as well as professional statistical tools such as Zhuizi.com, Jinhua.com, Ai stand.com and webmaster tools.