The invention discloses a criminal suspect investigation method for striking a window vertical to the ground by a circular projectile, which comprises the following steps of: calculating trajectory parameters to obtain a numerical value of an included angle gamma between an instantaneous speed V and a glass plane; measuring the numerical value of the included angle alpha between the long axis of the bullet hole image and the glass plane y '-axis; calculating an angle beta between a trajectory plane and a glass normal plane; using the trajectory parabola trajectory calculation module for calculating a trajectory parabola trajectory and a trajectory orientation module; establishing a longitude and latitude coordinate database of key personnel native places and in-situ living places; formulating a three-level search range; and suspects in different search areas are checked by adopting different means. The method is easy and convenient to operate and easy to implement, the trajectory parabola is accurately restored to the maximum extent, automatic searching and troubleshooting are achieved in the whole process, and manpower and material resources are saved. The position relationship between the location of the suspect and the trajectory of the projectile in the specific case can be displayed, so that searching and troubleshooting are more targeted; and the suspect levels of the suspects are divided according to the search levels, so that search and troubleshooting are more scientific.