Is it the some Caspian in voyage of dawn treader?

You're likely referring to Caspian X from The Voyage of the Dawn Treader, the fourth book in C.S. Lewis's The Chronicles of Narnia series.

While there is a Caspian Sea, which is a large saltwater lake in Asia, it is not the same Caspian as in the book.

Caspian X is a fictional character, the King of Narnia in the book. He is the son of Caspian IX, who appears in Prince Caspian. Caspian X is a wise and courageous ruler, and plays a key role in the story of The Voyage of the Dawn Treader.

Let me know if you have any more questions about Narnia!