He claimed he was protected by the "stand your ground" law in Florida which allows citizens to use lethal force if they feel they are in imminent danger of death or significant harm.
"The physical evidence contradicts the defendant's version of events", Barthle wrote in her ruling.
The confrontation began when Reeves became upset over Oulson's texting during the movie.
Reeves was arrested at the theater and charged with second-degree murder and aggravated battery, but was freed on bond.
The fatal shooting occurred on January 13, 2014, at a theater in a suburb north of Tampa during a showing of "Lone Survivor", the Hollywood dramatization of a US Navy SEAL unit's failed counterinsurgency operation against a Taliban leader in Afghanistan.
Some details of the interaction between Reeves and Oulson are in dispute.
In her ruling Barthle said the evidence showed a different story that was Reeves testified. Reeves returned without theater staff.
During a court hearing last month, Vivian backed her husband up by testifying she was "horrified" and "scared" because of how Oulson was behaving. Surveillance video shows Oulson throwing popcorn at Reeves. Oulson was shot in the chest.
"Because the defendant's testimony was significantly at odds with the physical evidence and other witness testimony, this court has considerable doubts about his credibility", Barthle ruled Friday.
According to the ruling, the court found that Curtis Reeves did not credibly demonstrate that he reasonably believed it was necessary for him to use deadly force in the situation.
More than 1,100 days have passed since Curtis Reeves shot and killed Chad Oulson in a Wesley Chapel movie theater.
Then-U.S. Attorney General Eric Holder renounced the Florida law after Zimmerman's acquittal and said it undermines public safety and likely encourages violence.