The invention discloses a desulfurization and denitrification process for boiler smoke. The desulfurization and denitrification process comprises the following steps: (1) boiler smoke enters a low-temperature smoke spraying wet-type integrated desulfurization and denitrification reaction tower from air inlets in the middle lower parts of the reaction tower and is in contact with desulfurization and denitrification slurry sprayed from a spraying layer to react in a rising process, the liquid gas ratio is controlled at 5L/m<3>-20L/m<3>, sulfur dioxide and nitric oxide in the smoke are absorbed, the smoke and the desulfurization and denitrification slurry fall back into a slurry tank, other gas continues to rise to pass through a demisting layer and a dust removal layer, enters a chimney through a gas outlet pipe and is discharged; (2) when the concentration of ammonium sulfite in the slurry which absorbs sulfur dioxide and nitric oxide is lower than 4wt%, the slurry is regenerated; and (3) the slurry is regenerated. The desulfurization and denitrification process is high in desulfurization and denitrification rates and good in treatment effect to existing boiler smoke, required absorbing slurry can be rapidly regenerated and reused, the comprehensive cost is low, and ultralow gas and liquid emission can be realized.