An　experimental　platform　for　drag　reduction　of　open　rotating　disk　system　has　been　constructed.　Combined　with　the　numerical　study,　the　drag　reduction　effects　of　spiral　grooves　on　rotating　disk　and　the　drag　reduction　mechanism　of　grooves　have　been　investigated　in　detail.　The　results　show　that　the　maximum　drag　reduction　ratio　of　6.1%　is　obtained　on　rotating　disk　with　the　7.4%　disk　surface　area　machined　with　spiral　grooves.　The　main　drag　reduction　mechanism　in　this　experiment　is　that　the　pressure　difference　of　the　two　sides　in　V-shaped　groove　creates　a　positive　torque.　Furthermore,　the　grooves　have　an　effect　of　increasing　the　pressure　difference　between　the　inner　and　outer　radius　of　rotating　disk.　Even　though　the　grooves　on　the　surface　of　disk　have　the　same　dimensionless　height　and　width　with　that　of　the　grooves　on　the　surface　of　flat　plate　where　drag　reduction　occurs,　it　increases　significantly　the　shear　stress　on　disk　surface.