Police said paramedics responded to reports of an unresponsive baby at the park at Daisy Hill, south of Brisbane, on June 14 last year.
The child was taken to Logan Hospital where he was declared dead later that evening.
Police arrested the Stretton man, 44, and a 36-year-old Zillmere woman after a 17-month probe into the baby's death.
Detective Inspector Mark White said the boy died after suffering injuries from "significant force" which were not caused by an accident.
"All I can say is the medical examination of the child disclosed significant internal injuries," he told reporters on Thursday.
"I actually won't go into the details, it's quite distressing.
"But it was quite clear, as at the end of that medical examination process, what the cause of death was."
Det Insp White said investigating the boy's alleged murder had been challenging for his colleagues "to listen, to read this information and speak to people about it".
The charged pair are scheduled to appear at the Beenleigh Magistrates Court on Thursday.
Det Insp White said despite the charges the case hadn't been closed yet, and he called for any witnesses or people who visited or lived in the caravan park around June 14 last year to contact police.
"Caravan parks have people that come and go ... maybe as as a resident, but also maybe visiting friends," he said.
"If someone may have been in and around there and we weren't aware of it at the time, if they could come forward, or someone may know these two people and may have had conversations with them, we'd be really interested to see what those conversations may have involved or articulated."
15°C