The invention provides an overall gasification fuel cell power generation system and method adopting supercritical CO2 bottom circulation. The system comprises a coal preparation unit, a gasifier, a gas cooler, a circulation gas compressor, an ejector, a fuel cell, a cathode air compressor, a cathode backheating device, a compressor, a pure oxygen burner, a CO2 gas turbine, a backheating device, awaste heat boiler and a turbine; on the basis of the overall gasification fuel cell power generation system, CO2 gathering is added, a CO2 cooling pressurizing device is utilized for converting CO2 gas into supercritical state CO2, supercritical state CO2 is adopted as bottom circulation to react with pure oxygen and tail gas at a fuel cell anode outlet inside the pure oxygen burner, generated high temperature and high pressure gas acts and generates electricity in the CO2 gas turbine; according to the structure, on the basis of efficient electricity generation of fuel cell electricity generation, the electricity generation efficiency is further improved; meanwhile, the system has the CO2 gathering function, and coal power generation CO2 emission reduction can be achieved efficiently withlow cost.