walk along和walk down這兩個短語都是“沿著.走路或散步”的意思,可以互換,意思上基本沒有什么區(qū)別.但常見　walk along that（ street）,walk down that（ road）.可見搭配上還是有一點區(qū)別,另外,口語表達中更常用walk down.
walk up 有兩個意思,一個是招呼人“快來看啊!”另一個是“走上前來,向.走過來”,比如有個人走過來和我說話,a strange walked up and talked to me.