"He has a smile on his face" 这个短语的来源源于描述人的表情，特别是脸上的表情。它是一个固定搭配，表示人面带微笑。
例句：
The salesman had a smile on his face as he greeted the customer.
(销售员面带微笑，向顾客问好。)
The pttle girl had a smile on her face as she opened her birthday presents.
(小女孩面带微笑，打开生日礼物。)