Thank you for reply !!
Just like you said, (I am not sure) I use the CJK language.
1) I have tried already to changing UTF-8, in the [tools]>[project option] as the following figure. Is it correct ?
2) To switch R language to English, I run the following code in the R Studio console. Is it correct ?
Sys.setenv(LANGUAGE="en")
3) I have run the R CMD check pkg.path instead of devtools::check() then the text garbling occur in the terminal, so I run the code chcp 437 for using English. Then the text garbling vanishes in the terminal. I want to do this with respect to R studio .