The　Heidong　ancient　man-made　underground　caverns　consist　of　21 single　caverns　and　the　group　caverns　cover　an　area　of　24,000 m2.　The　large-scale　underground　quarry　with　21 caverns　has　been　preserved　in　its　original　state　for　more　than　1400 years　in　Tiantai　County　of　South　China　due　to　the　favorable　engineering　geological　conditions　and　the　structural　integrity　of　rock　mass.　In　this　study,　based　on　the　field　investigation　method　and　numerical　simulation,　the　deformation　and　damage　of　the　surrounding　rock　of　each　ancient　cavern　chamber　were　studied,　and　the　damage　types　and　damage　mechanisms　of　the　surrounding　rock　were　analyzed.　The　influence　on　the　long-term　stability　of　the　cavern　was　analyzed　in　terms　of　ancient　engineering　concepts　and　the　quality　of　the　surrounding　rock.　Research　results　showed　that　cavern　block　instability　has　caused　some　roof　collapse　due　to　gravity　and　the　horizontal　displacement　conditions.　The　higher　quality　of　the　surrounding　rock　in　layers　6　and　8　is　an　important　reason　for　the　long-term　stability　of　the　ancient　caverns.　In　addition,　the　ancient　engineering　idea　implemented,　including　double-arched　structure　and　fault　avoidance,　as　well　as　waste　rock　accumulation　on　the　floor　of　the　caverns,　have　played　an　important　role　in　their　long-term　stability.　Overall,　this　study　is　relevant　to　modern　underground　engineering　seeking　to　promote　the　scientific　protection　for　ancient　engineering　constructions.　©　2022,　The　Author(s),　under　exclusive　licence　to　Springer　Nature　Switzerland　AG.