行若無事　

◎ 行若無事 xíngruòwúshì

[behave as if nothing had happened] 行:行動(dòng)、舉止。指在緊急關(guān)頭上能夠舉止鎮(zhèn)靜,毫不慌亂。也形容對(duì)事情聽之任之,無動(dòng)于衷