The invention provides a flow field measurement system and measurement method under model pitching movement. A first upper guide rail and a second upper guide rail are arranged on a water tank, lowerguide rails are arranged on a support, two trailers are arranged on the two upper guide rails, lateral connecting rods are arranged on a first trailer, first sliders are arranged on the lateral connecting rods, a second trailer is connected with reflectors through connecting rods, second sliders are arranged on the lower guide rails, sliding vanes are arranged on the first sliders and the second sliders, bases are arranged on the two sliding vanes, a laser device and a camera are arranged on each base, a horizontal connecting rod is arranged between the first trailer and the second trailer, athird slider is arranged on the horizontal connecting rod, a stepping motor and an encoder are arranged at the lower end of the third slider, the lower end of the encoder is connected with a force balance, and the lower end of the force balance is connected with a wing profile to be detected. The system and the method are low in cost, high in measurement efficiency, applicable to measurement of model dynamic pitching movement and also applicable to flow field measurement of a model in other specific dynamic movement modes.