The present invention relates to an HVDC thyristor-level damping resistor dynamic parameter online monitoring method. The method comprises: in each operation cycle of a damping loop, collecting one-side voltage value and a branch current value of a damping resistor in a conduction window period of a positive bypass thyristor and using the one-side voltage value and the branch current value of thedamping resistor for a conduction window period of a negative bypass diode, collecting the one-side voltage value and the branch current value of the damping resistor to use for calculation of a real-time resistance value of the damping resistor; and calculating the real-time resistance value of the damping resistor through only one voltage collection node and only one branch current collection node for each damping resistor in the window periods of the positive bypass thyristor and the negative bypass diode. According to the technical scheme of the invention, real-time detection of dynamic parameters in the operation period of the damping resistor is realized to provide a technical base for assessment of the whole operation state of a converter valve by operators in a convertor station and realize visualization of a state of the converter valve and daily monitoring so as to lay the foundation of improvement of usage efficiency of the converter valve.