In　this　paper,　in　order　to　explore　the　influence　of　indium　tin　oxide　(ITO)　size　and　mesa　shape　on　the　performance　of　GaN-based　micro　light　emitting　diodes　(Micro　LEDs)　on　sapphire　substrates,　Micro　LEDs　of　different　sizes　with　ITO　area　smaller　than　or　equal　to　the　light-emitting　area　were　designed　and　fabricated.　The　experiment　results　show　that　when　the　ITO　area　of　the　Micro　LED　is　equal　to　the　area　of　the　light-emitting　area,　its　optoelectronic　performance　is　significantly　better　than　that　of　the　Micro　LEDs　whose　ITO　area　is　smaller　than　the　area　of　the　light-emitting　area.　When　the　light-emitting　area　size　is　40　mu　m,　the　wall-plug　efficiency　(WPE)　of　the　two　structures　of　Micro　LEDs　can　differ　by　more　than　50%.　Based　on　above　experiment　results,　this　paper　designed　and　fabricated　Micro　LEDs　with　different　sizes　of　square　and　circular　mesa　with　the　same　ITO　area　as　the　light-emitting　area.　The　experimental　results　show　that　the　WPE　of　the　circular　mesa　Micro　LED　is　slightly　higher　than　that　of　the　square　mesa　Micro　LED　at　low　current　density.　However,　as　the　current　density　and　chip　size　increase,　the　performance　of　the　Micro　LED　with　a　square　mesa　is　better.