The invention provides a flight measurement system and a flight measurement method, and solves the technical problem that the existing RTK measurement system cannot perform accurate measurement in a sunken terrain. The system comprises a GNSS receiver used for receiving satellite signals and base station data chain and correction data to form positioning data; a laser ranging device used for measuring the height difference between the unmanned aerial vehicle and the ground when the unmanned aerial vehicle hovers to form correction data; and the unmanned aerial vehicle used for bearing the GNSSreceiver and the laser ranging device and controlled to be suspended to an appointed position. The hovering height of the unmanned aerial vehicle is utilized to avoid multipath interference of homologous wireless signals and improve the receiving sensitivity of the wireless signals. The relative height difference between the unmanned aerial vehicle and the measured position on the ground is obtained by using the mature technology of laser ranging to form correction data, so that the unmanned aerial vehicle can flexibly adjust the hovering height to overcome complex near-field obstacles, the positioning measurement precision of the ground position is ensured, and a reliable guarantee is provided for realizing flexible fixed-point measurement and range measurement.