I am watching TV now.
我正在看電視。
句型：主語+be（am，is，are）+現在分詞～.
Look！Nancy is doing her homework
看！南希正在做作業。
They are cleaning their classroom.
他們正在打掃他們的教室。
She isn't reading now.
過去進行時
He was walking in the park at that time yesterday
昨天那個時候，他正在公園散步。
句型：主語+be（was，were）+現在分詞～.
I was watching TV then.
那時，我正在看電視。
When I came home， they were cooking in the kitchen.
當我進家時，他們正在廚房裡做飯。
When he knocked at the door， we weren't doing our homework.
當他敲門時，我們沒有在寫作業。
Were you cooking at that time？
那時，你在做飯嗎？
現在進行時的用法： 其結構是助動詞be的過去形式is/are/am +v-ing.
其句式變化仍然要在be上做文章。
現在（說話的瞬間）正在進行或發生的動作，強調「此時此刻」。E.g. He is reading . They are talking now.
2、當前一段時間內的活動或現階段正在進行的動作。E.g. They are working these days.
3、某些動詞的現在進行時，表預定的計劃或即將發生的動作。E.g I am coming.
其結構為be+現在分詞. 現在分詞的變法有
1、一般在動詞詞尾加上-ing ,E.g. jump
2、以不發音字母e結尾的動詞，先去e，再加-ing. E.g have write
3、.以重讀閉音節末尾只有一個輔音字母結尾的詞，它前面是單個元音字母時要先將詞尾的輔音字母雙寫，再加上-ing. E.g. sit put
其句式變換都在be上做文章。
E.g. He is buying a bike.
Is he buying a bike?
He isn’t buying a bike.
一般由look,listen,now, at this moment等時間狀語做標誌。
4. 習慣進行：表示長期的或重複性的動作，說話時動作未必正在進行。
Mr. Green is writing another novel.
(說話時並未在寫，只處於寫作的狀態。)
She is learning piano under Mr. Smith.
5. 表示漸變的動詞有：get, grow, become, turn, run, go, begin等。
The leaves are turning red.
It's getting warmer and warmer.
6.與always, constantly, forever 等詞連用，表示反覆發生的動作或持續存在的狀態，往往帶有說話人的主觀色彩。
You are always changing your mind.
典型例題
My dictionary ___, I have looked for it everywhere but still___ it.
A. has lost, don't find B. is missing, don't find C. has lost, haven't found D. is missing, haven't found.
答案D. 前句是一個仍在持續的狀態，應用進行時，由於沒有找到，其影響仍然存在，應用完成時，瞬間動詞用於否定式時可用於完成時。