Abstract: The vibration characteristics of converter transformers under full-load operation has not been studied sufficiently. Therefore, the vibration on-line monitoring of converter transformers is carried out during the commissioning of a ±800kV project. Vibration data under the operations of DC load rising and full load are collected. Based on the collected data, the vibration magnitude, vibration main frequency and vibration power under DC load rising and full load are studied. Results show that: the vibration amplitude of different frequency shows a power function relationship with DC power that stabilizes first and then increases gradually. In light load stage, the top tank vibration is larger, while the load increases, the side tank vibration becomes larger. In the no-load and light-load stages, the main frequency of 200Hz accounts for the highest proportion, reflecting the main vibration frequency of the core. With the increase of load, affected by the harmonic current, the proportion of 400Hz main frequency gradually increases, reflecting the main vibration frequency of the winding. The variation of 300Hz vibration component is complex, and the converter transformers of different converter stations do not show consistent change characteristics. Under any load, the proportion of vibration power of converter transformer from high to low is 0-400Hz, 1000-2000Hz, 400-1000Hz and 2000-4000Hz, of which 0-400Hz accounts for more than 40%, 400-1000Hz is less than 15%, and 2000-4000Hz is less than 10%. It is shown that determining the operating conditions of DC system is a prerequisite for accurately evaluating the mechanical vibration conditon of converter transformers. Research results in this paper lay a foundation for qualitative and quantitative evaluation of mechanical vibration conditon of converter transformers in operation