Cell　instance　segmentation,　which　identifies　each　specific　cell　area　within　a　microscope　image,　is　helpful　for　cell　analysis.　Because　of　the　high　computational　cost　brought　on　by　the　large　number　of　objects　in　the　scene,　mainstream　instance　segmentation　techniques　require　much　time　and　computational　resources.　In　this　paper,　we　proposed　a　two-stage　method　in　which　the　first　stage　detects　the　bounding　boxes　of　cells,　and　the　second　stage　is　segmentation　in　the　detected　bounding　boxes.　This　method　reduces　inference　time　by　more　than　30%　on　images　that　image　size　is　larger　than　1024　pixels　by　1024　pixels　compared　to　the　mainstream　instance　segmentation　method　while　maintaining　reasonable　accuracy　without　using　any　external　data.　©　2023　SPIE.