Abstract: The lack of properly regulated UAVs interferes with the normal operation of flights and poses a risk to transportation aviation, and such problems will become more prominent with the booming UAV industry. To study the risk of collision between UAVs and manned aircraft in the terminal area, three scenarios are constructed: both UAVs and manned aircraft operate on the flight path; both UAVs and manned aircraft fly freely; and UAVs fly freely with manned aircraft approaching or departing. The first scenario uses the Reich model and assumes that the PBN and GPS positioning errors conform to a normal distribution, and uses the normal distribution function to calculate the collision probability. The second scenario uses the gas model and considers the effect of the manned aircraft velocity magnitude direction on the collision probability. Due to the limitations of the first two models, an improved collision model is proposed for the third scenario, and the collision probability between manned and unmanned aircraft is obtained by judging the 4D trajectory of manned and unmanned aircraft, combined with Monte Carlo method for simulation.