To extract most energy in a photovoltaic system, in addition to the conversion efficiency of solar cells, the maximum power point tracking (MPPT) unit plays a very important role. Generally speaking, the MPPT unit on a moving vehicle must keep high tracking accuracy under rapidly changing environment conditions. In this paper, some properties of PV system on a moving vehicle are discussed, and a modified quadratic MPPT algorithm is proposed. A theoretical analysis and the design principle of the proposed method are provided and its feasibility is verified by simulation results. This study also performed experiments on a model ship, and the experimental results confirm the superior performance of the proposed method.