Abstract: The radioactivity and the absolute gamma emission probability for the 641 keV main gamma ray of the short half nuclide ¹⁴²La were measured by DCC on a 4πβ-4πγ and a 4πβ-4πγ coincidence counting devices, and the standard uncertainty for the radioactivity measurement result is 0.46%, the emission probability of the 641 keV gamma ray is 0.473±0.005, which is only 0.24% lower than the data 0.474±0.005 proposed by the Table of Isotopes, 8th edition. The relative emission probabilities of the other main gamma rays were measured by another HPGe gamma spectrometer, which relative efficiency is above 60%, the measurement results are good. The half life of ¹⁴²La was calculated to be (91.0±0.7) min, which has a lower deviation of 0.2% than (91.1±0.5) min proposed by the Table of Isotopes, 8th edition.