I'm an US citizen and I'm going to get marry soon with my boyfriend who is an illegal, he is from Mexico, what can I do for him to be a citizen?

Once you marry, you can file an immigrant visa petition on his behalf. While deportation is always a risk when one is in the country without authorization, the risk is low unless he is arrested. Your husband will not be able to adjust status in the United States given his manner of entry. He will obtain a visa through consular processing. This will require him to obtain a waiver for his unlawful presence. This waiver is based upon hardship to you if you had to relocate to Necico or live apart from your husband. He will likely qualify for the provisional waiver, which allows him to have it approved before going to Mexico for a visa interview. You can read more about family immigration at http://myattorneyusa.com/family-immigration.