Wǒ ɡāi zǒu le.

我该走了。

I’ve got to go.

Notes:

我(wǒ): I

该(ɡāi): should

走(zǒu): to go, to walk

了(le): particle word which shows something happened.

Example:

A: 已经11点了，我该走了。

    Yǐjīnɡ 11 diǎn le, wǒ ɡāi zǒu le.

    It's already 11 o'clock. I have got to go. 

B: 好的。

    Hǎode.

    OK.