Thermal annealing and laser irradiation were used to study the activation rate of phosphorus in silicon after ion implantation. The activation rate refers to the ratio of activated impurity number to the total impurity number in the sample. After injecting phosphorus with the dose and energy (energy = 55 keV, dose = 3 × 10¹⁵ cm^–2), the samples were annealed at different temperatures, and laser irradiation experiments were performed after annealing. The experimental results showed that the activation rate of phosphorus was the highest at 850 °C, and the highest activation rate was 67%. Upon femtosecond laser irradiation samples after thermal annealing, while keeping the crystalline silicon surface without damage, the activation rate was improved. When the energy-flux density of the femtosecond laser was 0.65 kJ/cm², the activation rate was the highest, increasing from 67% to 74.81%.