The invention discloses an automatic pop-out side impact protective device. The automatic pop-out side impact protective device is suitable for a child safety seat and comprises force bearing mechanisms connected to side wings of a backrest of the child safety seat, and the force bearing mechanisms act relative to the side wings of the backrest and then have pop-out positions and folding positions; and the automatic pop-out side impact protective device further comprises an automatic control part, and the automatic control part bears force along with using of the child safety seat to drive theforce bearing mechanisms to act relative to the side wings of the backrest so as to be located at the pop-out positions. According to the automatic pop-out side impact protective device, in the usingprocess of the child safety seat, the force bearing mechanisms can automatically pop out to provide enough anti-impact protection against the side wings of the backrest to avoid the situation that the child safety seat cannot provide enough anti-impact protection against the side wings of the backrest due to the factors such as forgetting and inappropriate operation caused by manual operation, and thus the safety of the child safety seat is improved.