The paper proposes a novel method for online measuring the short-circuit impendence of the distribution transformers (DT). The relation expression of the short-circuit impedance with respect to the voltage and current of the primary and secondary side has been developed through the analysis of the equivalent circuit model of a transformer, in which the voltage and current of the DT is collected by 12-channel-data-acquisition unit. And the online SCI is computed by fitting the obtained voltage and current data. The simulation results and comparison illustrated that the proposed method is simpler and more efficient with high accuracy. Besides, the proposed method integrates the linear fitting technique. The simulation results based on Matlab/smulink verified the feasibility and effectiveness of the novel method for online measuring the short-circuit impendence of the DT.