It is the first time that he has been to China.
It is the first time for him to visit China.
This is his first time to have been in China.许老师你好，请问为什么您用的是完成时，而不是一般现在时？因为名词前有序数词修饰的时候后面从句一般用完成时态，也就是有时说的表示”某人第几个（次）做某事“要用完成时态