Measurement of τ mass at BESIII

τ mass is a very sensitive quantity in testing the lepton-universality. Moreover, as one of three elementary leptons in nature, the accuracy of τ mass is almost four orders of magnitude lower than those of electron and muon, whose accuracy is at the level of 10−8. Further improvement of the accuracy of τ mass is of great importance for particle physics. The new experiment at BESIII aims at the uncertainty less than 0.1 MeV, or 6 × 10−6 for the relative error. To reach this goal, the optimization study is performed to acquire the best strategy for the data taking. The recent progress of τ mass scan at BESIII is introduced.