Hello Zhiqiu,
Thank you for raising this question.
I would like to kindly ask you to elaborate a little bit more about which information you are trying to retrieve using JQL.
Per your description, I believe you are trying to return Stories that have a specific Epic linked to it, is that correct?
If that's what you are looking for, you can use the parameter Epic Link to do it:
"Epic Link" = issuekey
Where issue key is the id of your Epic.
Please, let us know if I've misunderstood your question and provide us more details about the feature you are needing
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