Indexes in MySQL are one of the key factors in optimizing database performance. When designing and implementing the data structure of the index, MySQL chose B+ tree as the main storage structure. This choice performs well in terms of query performance and disk I/O efficiency. However, B+ tree is not the only index implementation solution. Common alternative data structures include hash table, binary tree, B tree and skip list. This article will analyze the characteristics of these data structures in detail, compare their advantages and disadvantages, and focus on answering the questions about MySQL.