In order to research on collision risk of parallel runway with simultaneous instrument approach mode, First, through the investigation into the control process of Beijing Capital Airport controllers, the paper analyzes the moving state process of aircraft in simultaneous instrument approach mode. Secondly, based on the position error model, the equations of motion state of two aircraft with simultaneous instrument approach mode are established, and then the parallel runway collision risk model in simultaneous instrument approach mode is established. The key of the position error and velocity parameters in the model are based on the actual operation ADSB data, and the other parameters are ICAO recommended values or controllers experience values. Finally, the paper utilizes MATLAB software for simulating the collision risk of per moment in the whole process of simultaneous instrument approach mode, thus, obtaining the variation trend of the whole process, which provides support for the practical operation and future optimization of simultaneous instrument approach mode.