In order to explore the operation conditions of the new fixed-bed gasifier, the numerical simulation combined with experimental data was carried out. In the experiment, low-rank coal was selected, the average particle size of coal was 10 mm, the coal dosage was 35 kg/h, the oxygen dosage was 10 m3/h, and the operating pressure was set as 0.1 MPa to carry out the gasification test and get the data. Fluent dynamics numerical simulation and Aspen Plus thermodynamic numerical simulation were carried out respectively, which was compared with the actual test firing data. The results show that the absolute errors and the experimental values of the volume fractions of CO, H2, CH4 and CO2 in the upper outlet simulated by Fluent are 0.027, 0.010, 0.020, -0.057, respectively. The absolute errors between the simulated volume fractions and the test values of CO, H2, CH4 and CO2 at the lower outlet are -0.038, 0.007, 0.003 and 0.037, respectively. The absolute errors of the volume fractions and the experimental values of CO, H2, CH4 and CO2 at the upper outlet simulated by Aspen Plus and the experimental values are 0.025, -0.028, 0.012 and -0.009, respectively. The absolute errors between the simulated and tested values of CO, H2, CH4 and CO2 at the lower outlet are -0.022, 0.010, 0.002 and 0.010, respectively. Aspen Plus simulation results show that the absolute error of H2 volume fraction in the upper outlet gas is -0.028, and the absolute error of other components is ≤0.025. Therefore, this model is selected to further study the influence of O2 flow rate to coal mass flow ratio (O2/coal) and H2O to coal mass flow ratio (H2O/coal) on gas composition. It is found that when O2/coal is 0.328 and H2O/coal is 0.405, the gas output in the upper and lower sections exhibits good characteristics, and the heating value is higher than 11 MJ/m3, which can be used as the recommended operating parameters in the gasification process.