According to Indipendent.co.uk, the police officers attempted to revive the man with CPR before paramedics arrived at the scene, just after 11 am on Sunday.
The man gave up to ghost shortly afterwards.
The Merseyside Police said his death is being treated as unexplained but is not believed to be suspicious, a spokesperson for.
“The museum will remain closed for the rest of the day.
“Our thoughts are with the family of the deceased and an investigation into the death is ongoing, although it is not believed to be suspicious.
“There were a number of people, staff and visitors, in the museum at the time and they are assisting with the investigation.
“We understand that this is a distressing situation for both staff and visitors, who may have been traumatised by the incident and they are advised to contact 111 or their GP for support.
“Emergency services personnel affected by the incident will be supported by their relevant organisations.”
A woman was reportedly taken to hospital with minor injuries sustained during the same incident, according to The Liverpool Echo.
She was found “on the ground” inside the museum, according to the newspaper.
“National Museums Liverpool staff are working closely with Merseyside Police and helping them with their investigations,” a museum spokesperson said in a statement.
“Our thoughts are with the family at this very difficult time.”