Counterweight experiment of the dynamic balancing mechanisms of imaging roller was carried out according to rigid rotor dynamic balance principle for the varied characteristics of balance status of the roller. The imbalance principle and the basic rule of mechanism balance block’s movement and positioning in the drum rotation process was found based on the experiments. The purpose was to provide an experimental basis to resolve the roller imbalance resulting from the various plate sizes. The minor deficiency is that this counterweight experiment has some problems on testing, product assembling and equipment adjusting during working process, such as low precision and low efficiency.