Chidi Benjamin Uzomah Jr, 25, faces up to four years in prison if convicted of the stalking charge.
He was arrested after he appeared at the E! Entertainment Television headquarters and tried to see Ryan, whose radio show is produced at the location.
A restraining order petition filed by Seacrest's attorneys stated he was carrying a knife.
"His aggressive and violent efforts to come into physical contact with me are extremely frightening to me," Ryan wrote in a declaration for the restraining order. "They have jeopardized not only my personal safety, but also the safety and well-being of those around me."
Uzomah is already on probation after pleading guilty in September to assault, battery and carrying a switchblade knife in Orange County after he attempted to meet Ryan after an event and attacked one of the radio and television host's bodyguards.
Soon after his plea, Uzomah allegedly went to the offices of a radio station that airs Seacrest's morning show, not realising Ryan wasn't there. He then was arrested after showing up at the E! building last week.
Uzomah is a sergeant in the US Army Reserve and serves as a combat medic. He first joined Army National Guard in 2005 and was honourably discharged earlier this year, but returned to the Reserve in August.
Uzomah remains jailed on 150,000 dollars bail and is scheduled to be arraigned in Los Angeles.
Los Angeles County prosecutors also charged Uzomah with two counts of attempting to disobey a court order by trying to see Ryan.