Numerical simulations are conducted on dynamic evolution of the soliton molecules in an all-normal dispersion fiber laser. Peak-to-peak (PP) separation can be controlled by adjusting gain saturation energy (E sat ). Moreover, with the increase of E sat , the soliton molecules do not split into three bound states directly while it shows to avoid generating three bound states through a series of adaptive adjustments, thus we conclude that the soliton molecules have high nonlinearity tolerance. After adaptive adjustments each soliton has the same physical properties and a fixed PP separation to keep propagation. According to this paper, we can deeply understand the dynamic evolution of the soliton molecules.