In this study, commercial plant process simulation and HCNG mixing unit production and experiment were performed for HCNG commercialization through pilot plant scale-up. Process simulation were performed using the most common and efficient natural gas steam reforming. In addition, a method on how to supply HCNG was suggested through refueling experiment and production of mixing unit which was supplied with hydrogen and compressed natural gas. Supply of CNG for HCNG commercial plant uses the nationwide CNG infrastructure. Equipment for the production of hydrogen will be expanded to CNG infrastructure for the hydrogen supply. Equipment for the production of hydrogen was scaled-up to 300 Nm3/hr based on the pilot plant process simulation of 30 Nm3/hr hydrogen production. HCNG was satisfied with the emission acceptable standards of EURO-IV and its fuel characteristic is excellent because it is more eco-friendly than CNG. Soave-Redlich-Kwong equation of state was used as the thermodynamic model of process simulation. Langmuir-Hinshelwood and Power-Rate Law models were used as the reaction rate equation of the reactor. Mixing of HCNG was performed using ratio control. Amounts of the refueled HCNG was calculated after reading the pressure of refueling tank. The total energy efficiency for the respective pilot plant and commercial plant for production of hydrogen is 70%. Conversions of steam reformer and WGS reactor are 90% and 60%, respectively. The efficient operating conditions of this process are SCR=3 and GHSV=1500~3000 h-1. When operating intermediate pressure for hydrogen and natural gas are 63 and 55 bar, respectively, the required power in the case of multi-stage compression was lower than that of the single-stage compression and was reduced to about 25%.