Abstract: The researches on stress of new and old concrete joints were mainly from laboratory tests. And there was no prototype experimental study on the development law of early hardening age mechanics of new and old concrete joints in practical engineering. Although the existing simulation calculation program takes into account the development of early age hardening stress of new and old concrete joints, the rationality of the calculated stress can not be determined. In this paper, the prototype test of early age of new and old concrete joints in practical engineering is designed, and the strain and temperature diachronic curves of new and old concrete joints in this project are obtained, and the stress history curves of new and old concrete joints are calculated by using the existing elastic mold formulas. At the same time, according to the actual pouring plan, the temperature field and stress field of the concrete pumping station during the construction period are simulated and calculated, and then the correctness of the simulation results is verified by the prototype test data. The calculation results show that the temperature and stress history curves obtained from the prototype test are in good agreement with the simulation results, which proves that the existing simulation calculation program is accurate for the calculation of new and old concrete joints of mass concrete.