The radiation of positron annihilation in two aluminum samples from different origins was measured with the Ge(Li) detector. Using the 482 keV γ peak of 181Hf as reference, the relative positions of the annihilation peak centers were repetitively determined, the precision of the determination reached ± 6 eV. The results show that the rest mass of electron in these two different aluminum samples is consistent on 10 eV level.