Porous carbon materials were synthesized using biomass waste garlic-peels by two methods, precarbonization (GPC) and hydrothermal treatment (GPC/HT), in a pretreatment procedure. Brunauer-Emmett-Teller tests indicated that the surface area and total pore volume (at P/Po) of the GPC/HT are 4220 m2 g-1 and 2.02 cm3 g-1, higher than those of the GPC (2290 m2 g-1 and 1.02 cm3 g-1). The GPC/HT-S with a sulfur content of 87.6 wt.% exhibited a higher initial specific capacity (1087 mA h g-1 at 0.1 C) and better cycle retention (72.2% after 400 cycles at 0.5 C) than those of the GPC-S (65.3%). Optimized sulfur content was investigated to overcome the problems for shuttle phenomenon and low conductivity. Among the investigated samples (sulfur content of 65.3, 87.6, and 95.1 wt.%), the GPC/HT-S with 87.6 wt.% exhibited the best electrochemical performance. The enhanced electrochemical performance is attributed to the improved specific surface area of the GPC/HT and proper sulfur loading content, which effectively facilitated the intimate contact between sulfur and conductive carbon matrix and physically confined lithium polysulfide intermediates. The result in this work is important for using low cost and mesoporous bio-waste carbon as carbon framework for sulfur encapsulating in Li-S batteries.