Supercritical water gasification (SCWG) of biomass is a promising technology for hydrogen production. A novel pilot plant of SCWG that uses solar energy (henceforth SCWG-Solar) was constructed in State Key Laboratory of Multiphase Flow in Power Engineering to take SCWG a significant step closer to industrialization. The total throughput of biomass and water was designed up to 1 t/h. Life cycle assessment (LCA) was conducted to evaluate the environmental performance of SCWG-Solar process and its main environmental burdens. LCA was conducted using the SimaPro V8.2.3 software, and the Ecoinvent 3.0 database within the program. A sensitivity analysis on crucial parameters was performed to determine the environmental performance enhancement of SCWG-Solar process. LCA results showed that the SCWG-Solar system operation contributes approximately 58% to the total environmental impact. The construction of a solar concentrator mostly contributes to the environment emissions from the construction of the SCWG-Solar system. The environmental impact can be reduced by utilizing solar energy heated preheater and combining suitable post-treatment technologies of methane by-products with the SCWG-Solar system. The GWP decreases with the increase of feeding biomass slurry concentration and the GWP is close to a minimum when the biomass concentration reaches 30 wt%. GWP from the SCWG-Solar operation, which is 4.41 kg CO2-eq/kgH(2) for 1-MC process, is comparable to the solar based hydrogen production by two-step water splitting. Hence, the LCA in this study indicates that the SCWG-Solar is an environmentally friendly technology, although the system still has room for improvement.