Have a memory like an elephant.

　　A photographic memory.

　　eg：The boy has a memory like an elephant, he can tell you what happened in that period.

　　中英俚语俗语来源：晋书·苻融传：“持融下笔成章，耳闻则诵，过目不忘。”

　　反义词：丢三落四阳e a head like a sieve