Trump made the comments at a rally on Tuesday in Raleigh, North Carolina, a potential battleground state, according to presstv.ir.
The New York billionaire described the FBI decision announced earlier on Tuesday as the "best evidence ever that we've seen that our system is totally rigged."
“Everybody thought based on what was being said she was guilty. She was guilty. And it turned out that we're not going to press charges. It's really amazing," Trump said as the crowd erupted in a chorus of boos. "We have a rigged system, folks," he added.
Trump also made accusations that Clinton is "a criminal with a guilty conscience" and "one of the most crooked politicians in history."
On Tuesday, FBI Director James Comey said Clinton was "extremely careless" over her use of a private email server as secretary of state but did not recommend criminal charges against her.
Comey’s announcement concluded an investigation that began a year ago when the inspector general for US intelligence agencies told the Justice Department that he had found classified information among a small sample of emails Clinton had sent and received.
The Justice Department, which administers the FBI, had sought to complete the investigation and make recommendations on whether charges should be filed before the Democratic and Republican Party conventions take place later this month.
US Attorney General Loretta Lynch said on Friday that she would accept whatever recommendation she received from the FBI. The FBI’s recommendation to the Justice Department will have an enormous impact on the US presidential election.
Drawing on a report in The New York Times that Clinton "may decide" to keep on Lynch should she win the presidency in November, Trump accused Clinton of bribing Lynch.
"If she wins, she's going to consider extending the attorney general and you know what, I'm not saying, I'm not knocking the attorney general, what I'm saying is how can you say that? It's a bribe," Trump said.
"The attorney general sitting there saying, if I get Hillary off the hook I'm going to have four more years or eight more years, but if she loses I'm out of a job, it's a bribe. It's a disgrace. It's a disgrace."