Quark-hadron duality of three proton spin structure functions g1, g2 and gT are discussed simultaneously. It is found that the onsets of the quark-hadron dualities of g1p, g2p and g3p are similar and they are expected to be at about Q2 ～ 2 GeV2. In addition, our results show that the elastic peak remarkably breaks local quark-hadron duality.