Depending on the context, the word has two possible past tense forms — quit and quitted. When used to mean, “to leave” you can use both. For example, “Venu quit/quitted his job and moved to Chennai.”
The word “quit” can also be used to mean, “to stop”. We can, for example say, “Venu has quit gambling”. In this context, it is incorrect to use “quitted”. The word “quitted” is going out of fashion; it is mostly used in formal contexts.