In this paper, an advanced two-stage entrained-flow coal gasifier was built and its operational performance was examined. Detailed comparisons between exit gas compositions, consumptions of coal and oxygen, carbon conversion efficiencies, and cold gas efficiencies in single- and two-stage operational modes have been experimentally performed. The results showed that the coal and steam supplied in the second stage always contribute to more H-2 and CH4 while the CO concentration varies insignificantly. The two-stage process demonstrated potential technical and economic advantages compared to the single-stage process. The introduction of coal and steam in the second stage improves gas quality, reduces the coal and oxygen consumptions, and therefore, lowers the investment. However, there is an observed small decline in coal carbon conversion in the two-stage process.