Now I know the AWS RDS official documentation can realize the function read-only copy
For example:

RDS main library is the production of library, the library has three table (a, b, c), the main library use read-only create a copy from the library, then read only copy promoted to the database instance, the official link below:
https://docs.aws.amazon.com/zh_cn/AmazonRDS/latest/UserGuide/USER_ReadRepl.html

Will be read only copy after promoted to the database instance, if I want to make the new database instance what kind of steps to implement the following requirements by implementation:
New database instance has five table (a, b, c, d, e), including a, b, c should be three tables and the main library is consistent with the data table (equivalent to the three tables is a read-only copy of main library), and d, e two tables can modify it,