In this paper, elliptic flow is studied at a fixed centrality in Au+Au collisions at root s(NN)=200 GeV in the AMPT model. It is observed that as the participants increase, elliptic flow either increases or decreases at a different fixed impact parameter, but it does not have a trivial fluctuation. It is analyzed that the initial space anisotropy dominates the participant dependence of elliptic flow in near-central collisions(b=5 fm) and mid-central collisions(b=8 fm), while the interaction between particles can mainly answer for the elliptic flow behavior with the participant in peripheral co...
