The invention discloses a real-time monitoring device and method for power transmission line phase-to-phase spacer waving tension. The system comprises a data collection front unit, a phase-to-phase spacer device, a communication converting unit and an industrial personal computer; the data collection front unit comprises a first tension sensor, a second tension sensor and a control module, the first tension sensor is connected with a phase-to-phase spacer of the power transmission line phase A-phase B, the second tension sensor is connected with a phase-to-phase spacer of the power transmission line phase B-phase C, the control module is connected with the first tension sensor and the second tension sensor separately, and signals are sent to the communication converting unit in a wireless communication mode; the communication converting unit transmits the received data to the industrial control computer. The stress phenomenon of the phase-to-phase spacers is obtained in time, electric workers can conveniently improve the design and layout of the phase-to-phase spacers according to the phase-to-phase spacer waving stress phenomenon, the reliability and effectiveness are improved, and finally the phase-to-phase spacer anti-waving effect is improved.