The kinetics of ε-Cu particles dissolution in the matrix during welding of a copper-precipitation strengthening steel was determined by a combination of GleebleTM physical simulation, TEM examination and hardness measurement. The ε-Cu particles underwent a coarsening and part dissolution and then complete dissolution reaction as the peak temperature increased from 750 to 1 000 ℃, which resulted ir the decrease in the number density of ε-Cu particles and hardness in the heat-affected zone (HAZ). The results can be used to understand the evolution of this transformation and a softening behavior of the HAZ during welding of this type of steel.