Due to the harsh natural environment and the change in the arc of the cable itself will affect the transmission efficiency of the all-medium self-supporting(ADSS) cable, and some environmental hazards such as construction or ultra-high vehicles and fireworks will seriously threaten its normal operation, an ADSS optical cable sag online monitoring and environmental hazard warning algorithm is proposed. Firstly, the angle measurement method is used to monitor the radian in real time. Then, the detection algorithm of YOLOv4 is improved, and the visual intelligent fusion terminal is designed. Finally, the proposed algorithm is compared with other algorithms. The experimental results show that the average accuracy of the proposed algorithm is 96.43%, which realizes real-time monitoring, data processing, fault analysis and intelligent hidden danger alarm of the communication optical cable running state, and integrates into the ADSS optical cable online monitoring visual intelligent terminal.