The steady state design and economic evaluation for coal to synthetic natural gas (SNG) process is rigorously studied, and this study could give a baseline for design and analysis for SNG production in Taiwan or other countries relying on importation of an energy source. SNG is a product that holds very similar composition and heat value to typical natural gas, and can be used as a replacement in industrial and home usages. Natural gas is an important energy source in Taiwan, with increasing demand year by year. Because over 99% of our energy sources is imported in Taiwan, and because of the advantages of coal over natural gas (lower importation price, great abundance, easier transportation and storage, etc.), the process that converts coal into SNG is expected to benefit Taiwan if the related technology is successfully established. The whole process is divided into several parts, including air separation unit (ASU), gasification, the syngas treating section (water gas-shift reaction, syngas cooling, and acid gas removal), methanation reaction section, and electricity production block from upstream to downstream. The overall energy conversion efficiency for the plant is 60.38%, with the SNG production cost to be 10.837 (USD/GJ), thus this process will be economically and practically attractive.