The　mechanism　of　the　surface　depression　of　the　foam　glass　was　studied.　A　method　of　powder　sintering　with　plate　glass　as　the　raw　material　and　carbon　black　as　the　foaming　agent　was　adopted　to　investigate　the　influences　of　foaming　temperature,　soaking　time,　moisture　content　in　the　release　agent,　and　flame　preheating　temperature　on　the　surface　depression　of　a　foam　glass　blank.　The　results　indicated　that　insufficient　cooling　rate　and　rapid　foaming　process　that　could　not　react　synergistically　with　the　surface　tension　and　viscosity　of　the　glass　melt　aroused　the　mismatching　between　the　glass　melt　and　the　expansion　or　contraction　of　gas,　resulting　in　upper　surface　depression　of　foam　glass.　Besides,　the　batch　carbon　black　at　high　temperature　reacted　with　residual　water　in　advance　to　generate　large　amounts　of　gas　and　form　the　air　space　which　could　expand　inside,　leading　to　lower　surface　depression　of　foam　glass.