Professor McGonagall has several distinctive characteristics:

First of all, she is a fair tutor and treats the four colleges equally. Unlike Professor Snape, she would punish students of her own college severely even if they broke school rules, even if they lost the college cup in the end. I believe she will continue her principles of fairness as principal.

Secondly, she is a very strict, concisely spoken transfiguration teacher. All students respect (and partly fear) her, especially caring about Harry Potter. She did not tolerate any unruly behavior, and no one was allowed to interrupt during her class time - even Umbridge gained little benefit from interrupting her lectures. (See: "Harry Potter and the Order of the Phoenix")

At the same time, she is also a Quidditch fanatic. This proves her personality of being cold on the outside and hot on the inside. In the first grade, she caught Harry flying into the sky in violation of Mrs. Hoch's rules (to help Neville get his memory ball back). Instead of punishing him, she approved him to join the Gryffindor team.

In the end, she is a strong witch. Dumbledore passed away, the Second Battle began, and when Hogwarts was in turmoil, she still stood firm and worked hard to protect the students under the Death Eaters.

Professor McGonagall wears square glasses, has curly black hair tied into a high bun, wears dark green robes, and always shows a very stereotyped expression. According to author Rowling, she is a "vibrant" 70-year-old. The pattern of the square glasses she wears resembles the pattern of her transformed cat. She also loves Scottish tartan-style clothing, and her shirt is Scottish tartan.