Abstract: Condition monitoring and reliability analysis of HVDC converter become more important. The low-power wireless smart sensor technology is an effective means to realize the online monitoring of HVDC converter. It is necessary to solve the bottleneck of powering the sensor nodes. Based on the electrical and structural design of the HVDC converter in practical engineering, this paper proposes a miniaturized non-intrusive electromagnetic energy harvesting to power the sensor node that is used for online monitoring of thyristor temperature, The proposed energy harvesting takes advantage of the switch-on and -off transients. This paper firstly models and analyzes the magnetic field distribution in the space caused by the converter arm current. The design of the electromagnetic energy harvesting module is then proposed, and the key parameters such as the mutual inductance of the energy harvesting module are obtained by the combination of simulation and experiments. Furthermore, the equivalent circuit of the induction part of the electromagnetic energy harvesting loop is established, based on which the output voltage and power characteristics of the energy harvesting module are simulated. And the effectiveness of the proposed model is evaluated.