Coal pyrolysis to acetylene in hydrogen plasma is a clean process for the coal utilization. A gas-solid downer reactor was employed to facilitate the high temperature reactions of coal pyrolysis in milliseconds. The effect of the inlet design on the coal injection was studied using CFD simulations, which were qualitatively compared with the cold model experiments in the prototype of a 2 MW hydrogen plasma reactor. The results revealed that the distribution of the coal particles near the inlet nozzles was significantly influenced by the layout of the flat-shaped nozzles and the operating conditions. Accordingly the heating efficiency of the particles by the hot gas showed strong dependence on the inlet design. The hot model tests demonstrated that the reactor performance characterized by the concentration of acetylene in the product gas increased from similar to 7.6 to 9.6% by optimizing the nozzle design, which indicated the critical role of the nozzle design in the coal pyrolysis process.