Alkali-activated　fly　ash　geopolymers　(FAG)　exhibit　certain　limitations,　including　prolonged　hardening　time,　as　well　as　slower　strength　development　under　ambient　temperature　conditions.　Calcium　oxalate　can　significantly　shorten　the　setting　time　and　effectively　balance　the　compressive　strength　of　fly　ash　geopolymers　at　room　temperature.　Therefore,　the　properties　and　reaction　mechanism　of　FAG　doped　with　calcium　oxalate　at　room　temperature　were　studied　by　measuring　setting　time,　flowability,　compressive　strength,　and　using　various　techniques　such　as　calorimetry,　thermogravimetric　analysis　(TGA),　Fourier　transform　infrared　spectroscopy　(FTIR),　and　nuclear　magnetic　resonance　(NMR).　Results　indicated　that　calcium　oxalate　effectively　improves　the　hardening　properties　of　FAG.　An　appropriate　amount　of　calcium　oxalate　is　beneficial　for　the　28d　compressive　strength　of　FAG.　Further　increasing　the　content　of　calcium　oxalate　reduces　the　fluidity　and　compressive　strength　of　FAG.　Although　the　addition　of　calcium　oxalate　decreases　the　reaction　rate　and　cumulative　heat　release,　the　addition　of　calcium　oxalate　more　than　1　%　can　cause　the　hydration　reaction　curve　appearing　the　second　accelerated　exothermic　peak.　The　improvements　of　calcium　oxalate　on　the　hardening　properties　of　FAG　are　mainly　due　to　the　rapid　reactions　of　the　introduced　Ca2　+　with　OH-　and　the　dissolved　Si　structural　units　to　generate　C-S-H　gel　and　Ca(OH)2.　An　appropriate　amount　of　calcium　oxalate　can　improve　the　proportion　of　the　Alrich　structural　units　of　Q4(3Al)　and　Q4(4Al),　and　increase　the　mean　chain　length　(MCL)　of　the　formed　gel　products.　However,　due　to　the　strong　polarization　effects　Ca2+,　further　increase　the　content　of　calcium　oxalate　will　decrease　the　fraction　of　the　Al-rich　units　and　the　MCL　of　the　formed　gel.　For　this　reason,　total　proportion　of　the　oligomer　units　increases　and　the　compressive　strength　decreases.