1.表示正在进行的动作。
2.表示按计划安排即将发生的动作。例如：She is leaving for Beijing.她要去北京。
He is working as a teacher tomorrow.从明天起他要做老师。My father is coming to see me this Saturday.这个星期六我爸爸要来看我。
3.代替一般现在时，描绘更加生动。例如：The Changjiang River is flowing into the east.江水滚滚向东流。The sun is rising in the east.太阳从东方冉冉升起。
4.大多数动词可用于进行时，但也有些动词不用于进行时。常见的有：exist,live,understand,mean,owe,belong to ,know,doubt,suppose,remember,forget,
believe,trust,want,wish,refuse,like,hate,dislike,prefer,mind,hope等。
