Thank you for your reply and attempt, @vitor
Yes,the app 牛津高阶第9版 is not free and is an English-Chinese version of Oxford Dictionary, so I guess it can only be downloaded in mainland China because of the copyright.
Maybe I'm aware of what the problem is, which is that the app is not scriptable, rather than grammar errors. I'd tried to view its scripting dictionary in Script Editor but failed as Fig 1 shown. I also wrote the code below in Script Editor to validate, and it sent back "System Events got an error: Can’t set window "oxford_oalecd9" of process "oxford_oalecd9" to "hello"." So, I suppose I can't write a workflow as planned.
Fig 1
set theQuery to "hello"
tell application "牛津高阶第9版"
activate
end tell
delay 1
tell application "System Events"
tell process "oxford_oalecd9"
set value of text field 1 of group 1 of group 2 of group 1 of group 1 of group 1 of group 1 of window "oxford_oalecd9" to theQuery
end tell
end tell