The present disclosure relates to a process and a system for producing synthesis gas. The carbonaceous feedstock is gasified, in the presence of at least one of oxygen and steam, in a first reactor to obtain a gaseous mixture comprising H2, CO, CH4, CO2, H2O, tar and char. The gaseous mixture is treated in a second reactor, in the presence of a catalyst, to obtain synthesis gas. The system comprises a first reactor, a connecting conduit, a second reactor, at least one cyclone separator, at least one heat exchanger and at least one synthesis gas filter unit. The process and the system of the present disclosure are capable of producing synthesis gas with comparatively higher conversion of the unreacted char.