The expression on his face never changed.

他的面部表情总是一成不变。

《牛津词典》

There was a bored expression on her face.

她脸上有一种厌倦的表情。

《牛津词典》

The expression on his face changed from sympathy to surprise.

他脸上的表情由同情变成惊讶。

《柯林斯英汉双解大词典》

You can see the wisdom and experience in her face, which is very different from the baby's wondering expression.

VOA: special.2009.03.23

the face being drawn back in a universal expression that every human everywhere would be able to recognize.

用一种普遍的面部表情，脸被后拉,任何地点，任何人都能辨认。

耶鲁公开课 - 心理学导论课程节选

If you're stuck, if you're struggling, if you're not certain about something, please ask. We're not mind readers, we can't tell when you're struggling, other than sort of seeing the expression on your face, we need your help in identifying that.

如果你很差，如果你很纠结，如果你不确定某件事情，请问我们，我们不会读心术，我们没法儿看出来你们很纠结，除非能从你们的面部表情看出来，我们需要你们在这件事儿上的配合。

麻省理工公开课 - 计算机科学及编程导论课程节选

The woman laid in bed all day long with an agape expression on her face.

FORBES: The Death Panel Boogeyman

The expression on his face was vacant, stunned with sorrow, but before long he was smiling.

NEWYORKER: Mr. Bones

After lunchtime, her boss pulled up a chair with a grave expression on her face.

FORBES: What Not To Wear To Work This Summer