more than one直接做主语时,谓语用单数还是复数?

单数。

“more than one + 单数名词”虽有复数概念，但习惯上用单数动词。

e.g.:

More than one person is involved in this.
与此事有牵连的人不止一个。

类似的，“many a + 单数名词”也用单数动词。

e.g.:
Many a famous pop singer has been ruined by drugs.
很多著名的流行音乐歌手都因吸毒而毁了自己。