The invention discloses a small-radar-based mobile power transmission and distribution line anti-external-breaking monitoring method. The method integrates the visible light monitoring technology and the radar detection technology. According to the periodic occurrence characteristics of the external-breaking condition of a line pole tower or a line corridor with the existence of hidden external-breaking troubles, people timely hurry to an external-breaking easy-happening place through a mobile platform. In this way, a suspected object, which is approaching the line pole tower to destroy the line pole tower, can be identified, alarmed and repelled around the clock. The method is simple in implementation mode and high in operability and applicability. Through applying the method, defects existing in the traditional mode can be effectively solved. Therefore, the method provides a technical support and guarantee for efficiently preventing the external damage to the power transmission and distribution line.