Pinggu Peach Orchard is one of the largest orchards in Beijing, China, providing consumers with high-quality peaches. However, a large number of discarded peach branch waste was produced along with the peach production every year, which can cause environmental pollution and have potential safety hazards since they can only be burned or stacked on the roadside or in the field. Therefore, it is important and urgent to develop recycling techniques of discarded peach branches. In this study, peach branches-cellulose nanofiber (PB-CNF) was prepared by high-pressure homogeneous (HPH) from discarded peach branches and used as a reinforcing agent to enhance mechanical performance and adsorption capacity of the gelatin hydrogel. The variations on morphological, physic-chemical, and thermal characteristics of the PB-CNF were closely related to the cycles of HPH. Rheological properties of gelatin and PB-CNF were studied to understand the viscoelastic properties as well as gelling and melting temperature of the hydrogel. The results suggested that the HPH treatment was applied to produce PB-CNF with 5 nm in diameter, low crystallinity, and uniform dispersion. PB-CNF under HPH mixed with gelatin in an appropriate ratio of 1/4 can easily obtain a stable hydrogel system, which contributed to improving the mechanical performance and adsorption capacity of the hydrogel. Therefore, the waste peach wood can be used as raw material to extract and prepare a reinforcing agent (PB-CNF).