The invention relates to a synergistic biological treatment method for washing waste water and amine salt waste liquor produced by capturing CO2 in smoke of a coal-fired power plant. Waste amine salt in amine salt waste liquor produced by a regenerating tower in a flue gas CO2 capturing process is taken as one organic carbon source in a biological treatment process, an anaerobic and aerobic two-stage biotreatment is adopted for treating the washing waste water and the amine salt waste liquor, the washing waste water and the amine salt waste liquor are pumped into an anaerobic biological reaction column by a water pump, nitrate is converted into N2 under the action of denitrifying bacteria, sulphate is converted into S<2-> under the action of Desulfovibrio, organic carbon in organic amine salt is taken as a partial organic carbon source for sulphate reduction bacteria, and amine is converted into ammonia nitrogen. Waste water after anaerobic treatment enters an aerobic biological reaction column, nitration and denitrification of ammonia nitrogen are realized by carrying out intermittent aeration by an air pump, and finally ammonia nitrogen is released into the air in the form of N2; S<2-> generates sulphur under the action of thiobacillus thioparus, simple substance sulphur is recycled by a sulphur separator, and separated waste liquor returns to a washing tower to be recycled; and no pollution is produced in a CO2 capturing process.