Precise　online　measurement　of　cable　diameter　and　length　will　ensure　stability　of　quality　production　and　production　speed.　This　paper　describes　a　measuring　device　to　measure　cable　length　and　diameter　simultaneously,　accomplish　online　production　process　control.　The　device　consists　mainly　of　a　synchronous　sampling　part,　calculation　and　control　part.　The　synchronous　sampling　part　consists　of　two　parallel　rollers　one　meter　far　from　each　other.　A　measuring　band　cinctures　the　rollers　and　move　together　with　them.　There　are　two　electromagnetic　chucks　on　the　measuring　band　which　are　controlled　by　two　photoelectric　position　switches　to　hold　or　release　a　cable,　in　order　to　make　the　cable　move　with　measuring　system　synchronously.　An　optical　encoder　is　connected　to　one　of　the　rollers　coaxially　to　measure　cable　length.　For　cable　diameter　measurement,　two　orthogonal　CCD　sensors　are　used.　Accuracy　of　online　diameter　measurement　is　mainly　affected　by　vibration　of　cable　movement.　In　order　to　reduce　the　cable　diameter　measurement　error　caused　by　vibration,　measuring　system　uses　a　mechanical　damping　device　and　high-speed　CCD　sensors　which　exposure　time　is　up　to　microseconds.　The　calculation　and　control　part　of　measuring　device　can　filter,　amplify　and　binarizate　electrical　signals　from　synchronous　sampling　part,　then　they　are　processed　by　microcontroller　8051　to　complete　cable　length　and　diameter　measurement.　As　well,　the　measuring　device　can　set　error　limits　and　detect　online　whether　cable　length　and　diameter　size　are　in　default　range,　if　not　it　would　give　corresponding　alarm.