I tried to search the MarkDown files containing some specific text under the working directory, so I used the command below:
find . -name "*.md" | xargs grep "interpretation"
However, though I got the result what I need, the terminal also print out much errors like below:
grep: Problem: No such file or directory
grep: Solving: No such file or directory
grep: with: No such file or directory
grep: Algorithms: No such file or directory
……
etc
I wrote my solution as a answer below.