Water trees are one of the leading causes of cable insulation deterioration. Without timely treatment, the power cable with water trees faces the risk of breakdown and threatens the safe and stable operation of the power grid. Thus, it is necessary to study the mechanisms and factors that influence the growth of water trees. This paper presents a dynamic simulation method of the water tree’s growth based on energy calculation. The simulation results of the water trees with increased deterioration time are compared with the experimental data to prove the method's validity. Meanwhile, this paper explores the influence of applied voltage and frequency on the growth of water trees and analyses the growth mechanism with energy as the medium. The results show that increasing the voltage has a more significant effect on the morphology of water trees in the early stage of development (before 15 days). Increasing the frequency accelerates the overall growth rate more significantly (from 2.5μm/d to 6.1μm/d).