The invention relates to the field of monitoring and particularly relates to an online monitoring method and device for mechanical characteristics of a high voltage disconnecting switch operating mechanism. The method comprises steps of S1, collecting working current of a motor by a current transformer, drawing a current-time curve, and determining whether the operating mechanism has a fault and atype of the fault; S2, collecting angular displacement of the motor by an angular displacement sensor, drawing an angular displacement-time curve, determining whether the operating mechanism has a fault, and determining a position of the fault by combining the current-time curve drawn during monitoring; and S4, obtaining a final determining result of the operating mechanism according to preliminary determining results of the operating mechanism in S1 and S2. The method has the following beneficial effects of indirectly monitoring mechanical characteristics of the high voltage disconnecting switch operating mechanism online according to working current of the motor and a rotation angle of the motor, and determining a fault by using a testing manner combining two methods, so as to improve online monitoring reliability and avoiding misjudge.