The invention provides a large weight automatic calibration device used for mass transfer calibration. A cross beam assembly is provided with an equal armed lever cross beam. One end of the equal armed lever cross beam is connected with a first longitudinal arm while the other end is connected with a second longitudinal arm. The first longitudinal arm is provided with a weight picking mechanism and a weight rod connected with the weight picking mechanism. The weight rod is sleeved with a taring weight. According to the invention, a comparison transfer principle in mass transfer is adopted, mass comparison of a standard weight and a to-be-calibrated weight is performed on a weighing plate by utilizing an electromagnetic balance, in a condition of acquiring parameters including the standardweight mass value, the material density, temperature, air density, atmosphere and the like, through a mass difference value obtained through comparison and with the aid of a reasonable mathematics model, a reduced mass value or a reduced mass medication value of the to-be-calibrated mass is obtained. Therefore, smart and automatic large weight calibration is realized.