The Lion, the Witch, and the Wardrobe is filled with rich characters, and that is an amazing thing considering how short the book is. I would say that Peter, Susan, Edmund, and Lucy are the four main characters. These four children are brothers and sisters, and the story revolves around their adventures and conflicts in the magical land of Narnia. Along the way, they meet all kinds of various characters that help them. However, Aslan stands out as much more central and pivotal to the story than any other Narnian. Aslan is a lion, and he is the king of Narnia. At one point in the story, he sacrifices himself to the White Witch in order to rescue Edmund from her. The White Witch is the final major character in the story. When the story begins, she is ruling Narnia. She is quite evil, but she convinces Edmund that he should work for her.
As for the minor characters, I would say the most important are Mr. Tumnus, Mr. Beaver, and Mrs. Beaver. All three of these characters have pivotal impacts on the story. However, their characters are not as well developed as the major characters. The giant Rumblebuffin is a favorite minor character of many due to his kind and gentle manners. Maugrim is the White Witch's head soldier, and she also employs a dwarf whose name we never learn to drive her sleigh. Finally, the Professor is a minor character of some importance because he is the owner of the house and wardrobe where the children are staying. He is also the person that convinces Peter and Susan that Lucy might not be lying.
The major character in The Lion, the Witch, and the Wardrobe are the four Pevensie children: Peter, Susan, Edmund, and Lucy. The most predominant of the four, though, are Lucy and Edmund. It is Lucy who first enters the wardrobe and meets Mr. Tumnus the faun. Edmund acts as a foil for Lucy and also enters the wardrobe only to meet the White Witch. Jadis, the White Witch is the self-proclaimed "Queen" of Narnia and acts as the antagonist of the novel. Aslan, the lion, leads Narnia to breaking free from the White Witch's power after he offers himself in sacrifice.
Minor characters include Mr. Tumnus the Faun, Mr. and Mrs. Beaver, Maugrim the Captain of the Witch's Guard, and the Professor who accepts charge of the Pevensie children after their evacuation from London.
You can find excellent descriptions of the characters at eNotes. Just follow the link pasted below. The main characters are the Pevensie children, Aslan, and the White Witch. There are several minor characters.