The invention discloses a device for preventing accidental movement of an elevator car. The device for preventing accidental movement of the elevator car comprises a mechanism for preventing accidental movement of the elevator car and a locking plate, wherein the mechanism for preventing accidental movement of the elevator car is arranged on an elevator car roof, and the locking plate is fixedly connected to an elevator car guide rail. A transverse locking hole is formed in the locking plate. The mechanism for preventing accidental movement of the elevator car comprises a motor, a speed reducer, moving belts, a moving belt supporting frame, an elevator car fixing support plate, an elevator car fixing support, a movement locking device for preventing accidental movement of the elevator car,and a locking insertion plate. According to the device for preventing accidental movement of the elevator car, the motor drives the left moving belt and the right moving belt to move on the moving belt supporting frame, and the movement locking device can drive the locking insertion plate to enter or retreat from the transverse locking hole. The device for preventing accidental movement of the elevator car has important significance for ensuring the safety of elevator equipment and the personal safety of passengers, has the advantages of being simple in structure, safe, reliable, capable of being installed conveniently and flexibly, and the like, and has remarkable practical value for improving the safety of existing elevators.