Kieran Richardson, of Northallerton Road, Brompton, North Yorkshire, made the threats on Twitter ahead of the game at Fratton Park on May 16.
-> Government takes action on military suicides after JPIMedia campaignHis comments prompted the club to increase security measures and reassure fans who were attending the match.
Richardson was arrested on the day of the game and pleaded guilty to making a malicious communication at a hearing at York Magistrates' Court in June.
He was sentenced on Monday July 1 to a 12-month community order, with a three-month curfew and 25-day community rehabilitation requirement, court staff said.
North Yorkshire Police said Richardson posted two tweets on May 15 in response to a message by a Portsmouth fan about throwing a smoke bomb at Sunderland supporters.
He wrote: "I wonder how many Portsmouth fans I can shoot. Everyone remember the Manchester Arena bombing, just imagine Fratton Park going bang.
"Well, let's find out tomorrow. PS I'm hoping to kill at least 150 Portsmouth fans, fingers crossed."
In another tweet, he wrote: "Bomb, bomb Fratton Park, the Portsmouth fans will die. Going to be fun tomorrow."
-> Bus privatisation attacked as transport chief hints at changes for First and Arriva bus networksIn response to the messages, Portsmouth FC and Hampshire Police made statements reassuring fans that increased policing and security would be in place at the match.
A Portsmouth spokesman said: "Portsmouth Football Club are aware of a message that has been posted on social media and are working police on this matter.
"The club would like to reassure fans that there will be enhanced security checks in place for Thursday's play-off match against Sunderland at Fratton Park."
Court staff said Richardson was ordered to pay an £85 surcharge and £85 costs.