One-step catalytic gasification is an emerging technology for the production of synthetic natural gas (SNG). However, limited information is available regarding the process simulation and system analysis of the entire process from the system level. In this study, an entire process model of catalytic gasification for SNG production was developed, and the corresponding process optimization and energy and exergy analyses were conducted. To achieve high methane production, the gasifier should be operated at a gasification temperature ≤1023.15 K, gasification pressure ≥30 atm, and water-bagasse ratio ≈0.35. Under the typical catalytic gasification conditions (973.15 K and 35 atm), the molar fraction of methane and the high heat value of the final SNG were 87.7% and 36.44 MJ/Nm3, respectively. The highest energy and exergy inputs, 50.72% and 50.03%, respectively, were derived from the methanol employed in gas purification. The second highest energy and exergy inputs, 38.31% and 40.63%, respectively, were derived from bagasse. The total irreversible exergy loss accounted for 8.22% of the total exergy output, which was mainly consumed in catalytic gasification and gas purification at proportions of 69.0% and 29.02%, respectively. The total energy and exergy efficiencies of the entire process were 34.64% and 33.91%, respectively.