Abstract: Condensation caused by high-humidity environment is one of the main reasons for the insulation failure of high-voltage switchgear. Therefore, based on the study on the condensation development characteristics of KYN61−40.5 high voltage switchgear, a heater arrangement method, in which the temperature rise, temperature rise uniformity, dehumidification effect and total power consumption are comprehensively taken into consideration, is proposed in this paper. First, the test of condensation development characteristics inside the switchgear under humid environment is carried out in an artificial climate chamber. Secondly, the effective heating space and heating uniformity of different heaters are comparatively studied. Then, the optimal scheme for heater arrangement is obtained based on the comprehensive evaluation function and experimentally verified. Finally, combined with the electromagnetic-fluid-temperature multi-physics numerical simulation, the influences of load current on the distributions of temperature and humidity inside the switchgear and the moisture condensation mechanism of the switchgear are discussed. The results show that the current transformers in the cable room are the parts prone to condensation. The silicone rubber heater installed in the form of a bracket has the best effective heating space and temperature rise uniformity. The optimal scheme for heater arrangement can remove condensation within 8 hours without causing overheating of insulating components. The results can provide reference for the condensation mechanism analysis and heater arrangement of high voltage switchgear.