[en] For the emergence of Berry geometric phase, the authors analyze the relevant physical background condition of the weak transitions among quantum energy-levels. The authors elaborate a further discussion on the internal relationship between the strict obtainment of Berry geometric phase and the weak transitions. The study shows that the strict obtainment of Berry geometric phase is the natural result of the adiabatic limit effect of weak transitions among quantum energy-levels. These transitions occur inevitably during the evolution process of quantum system