He found his hometown greatly changed 怎么样改为主从句形式？
He found his hometown greatly changed. 过去分词作宾补为被动意义。
假如要表示主动意义，则不可以用changed过去分词作宾补，而应该用that从句：
He found that his hometown had greatly changed. 主动意义。
所以，你的句子假如改为that从句，要用被动语态。
He found that his hometown had been greatly changed.