He studied in Central College, which is now be known as Queen's College.

be 是系动词原形，表示"是"的状态。 known 是动词 know 的过去分词形式，know 意思是"知道、了解"。 as 是介词，表示"作为、以...身份"。 be known as 是一个固定短语，意思是"被称为、以...著称"，用来表示某人或某物被广泛认可的名称或称号。