簡單初級的講：
need to do 需要做某事
need doing 是需要被做有被動的意思
如;I need to wash my clothes.My clothes need washing.
need doing = need to be done
I need to mend my bike.My bike needs mending.
具體的說：
need to do sth實義動詞
need doing sth,表示被動
人＋need ＋to do
物＋need ＋doing
物＋need ＋to be done
請看下面的例子：
1．We need to collect the parcel before we leave for England．去英國之前,我們需要收拾好行李.
2．We need to tell him the truth．我們需要告訴他真相.
3．My car needs repairing．我的汽車需要修理.