The invention discloses a portal crane anti-collision method. The portal crane anti-collision method includes the steps that firstly, a running signal is received, and running starts; secondly, a portal crane system is initialized; thirdly, the voltage of the portal crane system is detected by a detection module, and the state of the portal crane system is judged; fourthly, if the portal crane system runs normally, the monitoring module keeps real-time detection; and if the portal crane system is low in voltage, the detection module sends a signal to an intelligent control module; fifthly, when the intelligent control module receives a detection module signal, the portal crane system is in a running state, then the intelligent control module turns off PWM of the portal crane system, and after the portal crane system stops running, a relay is turned off; and the portal crane system is in a stop state, the intelligent control module directly turns off the relay, and running of the portalcrane system ends. According to the portal crane anti-collision method, due to the detection module and the intelligent control module, when an elevator door is opened and closed, if a power failuresuddenly happens, under the effects of a door heavy punch, the elevator door cannot be fast closed to generate colliding, the elevator door can be closed slowly, and the effect of safely protecting passengers is achieved.