Aimming at the technological actuality of surface flow velocity measurement, a novel noncontact photoelectric measuring method for surface flow velocity is proposed. By deducing scattered light intensity formulae, it is concluded that scattered light intensities modulated by both up and down stream shallow sediments have cross-correlated characteristics based on sediment succession effect in shallow water.A formula for flow velocity measurement is derived and the effects of the measuring distance between up and down streams,flow velocity and sampling ratio on the measuring results are analyzed based on the cross-correlated characteristics.Then,an experimental system is set up, and the flow velocities are measured at 6 different flow rates in the cases of 6 sediment concentrations. The experimental results show that the measured flow velocity is coincident very well with the calibration flow velocity under six different sediment concentrations,which proves the feasibility of measurement theory. Experimental results also show that the absolute errors can be controlled to less than 8% and the correlative errors within 8% under the circumstances of suitable sediment in liquid.