The main characters, I would argue, are Milkman Dead, Pilate Dead, and Guitar. The novel focuses on Milkman and his search for individuality, his identity, and escape from his present. Guitar, his friend, and Pilate, his aunt, create the core of Milkman's understanding of the world in that he spends the most time with them, travels with them and learns from them.
The secondary characters are Macon Dead, Milkman's father, Hagar, Milkman's girlfriend and Pilate's granddaughter. In addition, I would add Susan Byrd and Circe, who provide Milkman with information about his past.