Purpose　-　The　purpose　of　this　paper　is　to　detect　and　control　the　liquid-level　of　stereolithography　apparatus　precisely.　Design/methodology/approach　-　A　brightness-variable　laser　source　is　adopted　to　remove　the　computational　error　of　divider　and　a　closed-loop　circuit　is　set　to　measure　the　terminal　voltage　directly　proportional　to　the　output　current　of　photosensitive　devices.　It　employs　a　sinking-block　device　to　control　the　liquid-level.　Findings　-　The　precise　calibration　result　of　this　detecting　device　indicates　that　the　resolution　of　the　liquid-level　detection　can　reach　+/-　1.5　mu　m.　Originality/value　-　This　sinking-block　style　liquid-level　control　device　can　allow　for　the　liquid-level　wave　reduced　from　+/-　45　to　+/-　15　mu　m.