您快到了！您要做的就是逃避重复括号:

You were almost there! All that you have to do is escape the repetition braces:

sed -e 's/[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}/x.x.x.x/g' test.txt