Question: Can my dad get a green card to immigrate to the US? How?
Question Detail: I am 20 years old and am going be 21 in July 18 I am a US citizen with my mom and my dad lived in US for more than 15 years but he got deported for a domestic violence case with my mom but he being in Dominican Republic for more than 6 years so I am asking if he could get a his green card back and in case yes, in how long?

Answer: You should consult with immigration lawyer because your father's case sounds complicated and you dont want to make a move(or not to make a move) without an advise from counsel. 

Generally, if your father was deported due to his criminal conviction, it will be hard for him to immigrant back to the US again.  He may apply for non-immigrant visa in certain cases.