"You say you want to make America great again but we all know what that really means," Miller said Wednesday on Comedy Central's "The Nightly Show with Larry Wilmore. "Ban Muslims, Mexicans are racist, Black lives don't matter. Make America great again? I think you want to make America white again."
Miller, whose 2011 Billboard-charting hit "Donald Trump" pushed him to fame in 2011, pleaded with his fans not to vote for Trump and voiced his support for the Black Lives Matter movement in December.
"I come here today as a white man, with the hope that maybe you'll listen to me," Miller said. "In other words, let me whitesplain this to you, racist s-- of a b---. You see, you're lowering the bar for our nation's intelligence. Your only goal is to stay in the spotlight no matter how much it fuels the fire of hate groups that you apparently know nothing about like the KKK and neo-Nazis."
Miller was referencing Trump's interview with CNN's Jake Tapper last month in which Trump stumbled over a question about an endorsement from former Ku Klux Klan grand wizard David Duke.
"I don't know anything about what you're even talking about with white supremacy or white supremacists," Trump said. "So I don't know. I don't know -- did he endorse me, or what's going on? Because I know nothing about David Duke; I know nothing about white supremacists."
When asked about his comments Trump blamed a "bad earpiece," and repeatedly disavowed David Duke's endorsement.
"I think you're just such an egomaniacal, attention-thirsty, psychopathic, power-hungry, delusional waste of skin and bones that you'll do, say or allow anything if it means you'll just get one more minute in the limelight," Miller said.
CNN has reached out to the Trump campaign for comment.
The tumultuous relationship between Miller and Trump began when Trump threatened to sue the rapper for using his name in his song.
"So you wanted to sue me but then you realized you can't sue somebody just for being super talented and incredibly good looking," Miller joked Wednesday.
While Trump has boasted about how many plays the "Donald Trump" song has on YouTube, he slammed "Little Mac Miller" on Twitter in 2013 for using his name without permission, calling him an "ungrateful dog" and demanding that Miller pay up for using him name.
"Little" is also a word Trump used on Twitter to slam Republican presidential rival Sen. Marco Rubio.