Sixth-tier club Poole Town need to raise £70,000 to upgrade their home ground by the end of March.
Austin, 27, has told Poole's board they can have free use of his box at Southampton's St Mary's Stadium to entertain potential investors.
He scored 48 goals in 42 games for the Dorset club between 2008 and 2009 before moving to Swindon Town.
Poole are a point off the play-off places in their first season in National League South. Their home ground Tatnam, in the grounds of a secondary school, is set to be graded by an inspection.
The club will be relegated should they fail to pass the inspection, which requires a minimum amount of terracing for standing and upgrade their floodlights.
"It's a massive ask for those of us running the club to maintain our National League position from a financial point of view," vice-chairman Chris Reeves told BBC Radio Solent.
"On the pitch, the team have done us proud. But, we have to comply with the ground grading issues.
"It just doesn't bear contemplation that we would be relegated," Reeves added. "Somehow or other, we've got to bridge this gap."
The club have raised nearly £1,000 in the first 24 hours since launching an online donations page for the improvements.
Southampton striker Charlie Austin is supporting one of his former non-league clubs in their bid to avoid demotion.