Aiming at the problem of collision risk between approaching and departing aircraft, the real distance and measurement distance between the two aircraft generated by the probability of position error, is analyzed.The degree of collision risk between the two aircraft is evaluated, and the collision risk of the two aircraft in the one descent mode is analyzed from three dimensions.A three-dimensional collision risk model on position error is established in combination with the adverse environmental factors of the go-around scene. In this way, it is of great practical and theoretical significance to explore the influence of close parallel runways on the safety interval between take-off and departure and approach landing aircraft.