Dissolution is one of the key processes during corrosion. To better understand and quantify dissolution in metallic materials, chemical dissolution activation energy is a key parameter. However, this value is difficult to obtain due to the challenge determining the transition state of dissolution from metal atom on surface to ion in solution. Here, a combined DFT and molecular dynamics (MD) framework has been built to calculate Ni dissolution activation energy in water. First, DFT is used to investigate the dissolution of an adatom from Ni(111) surface with constrained minimization approach, which gives a good picture of the bond breaking process between metal-metal atoms. Then, a MD simulation is applied to calculate hydration process of Ni atom interacting with H₂O molecules. Finally, by integrating these two parts together, a complete picture of dissolution process and the value of dissolution activation energy can be obtained. This study will lay foundation for higher scale modeling of dissolution process of pure metal and alloys, and also provides key parameters for pitting theory validation.