A coal co-gasification method, comprising the following steps: 1, fuel and a first pressurised oxygen-containing gas are injected into a gasifier, and the fuel is ignited so as to increase the temperature inside the gasifier; 2, when the temperature increase reaches a temperature capable of igniting coal-water slurry to be injected, injection of the fuel and the first pressurised oxygen-containing gas is stopped, and the coal-water slurry and a second pressurised oxygen-containing gas are injected into the gasifier so as to perform coal-water slurry gasification; 3, once the coal-water slurry gasification has stabilised, a third pressurised oxygen-containing gas and carbon dioxide carrying powdered coal are injected into the gasifier to perform co-gasification. The method operates stably, and overcomes cumbersome and time-consuming adjustment steps in the prior art.