In the operation of a photovoltaic system, one of the most important issues is absorbing maximum power from the PV array under continuous and rapid changing irradiance condition. The sampling points obtained at different moments are not on the PV characteristic curve with the same irradiance, so the MPPT strategy may misjudge. In this paper, a novel method to track the MPP is presented, which is based on three-point disturbance observation. The proposed algorithm utilizes three operating points that work in different duty cycle, using two points to restore a virtual operating point which is the same PV characteristic curve as the rest of the point. The proposed algorithm suppress the oscillation and misjudgment problem of traditional P&O method. And simulation and experimental results validate the performance of the proposed algorithm under continuous and rapidly changing irradiation conditions.