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In recent years, the removal of hexavalent chromium by green iron nanoparticles (FeNPs) has attracted attention due to the environmental friendliness, low price, and good durability of this adsorbent. In this paper, a new synthetic method was developed and optimized under the aspects of improved synthesis yield and Cr(VI) removal. For the first time, peel extracts of yali pear and FeSO4were employed in the synthesis of FeNPs (YL-FeNPs), and the synthesis conditions were optimized for five factors including extraction temperature, extraction time, peel mass, Fe2+-extract ratio, and drying method. For optimized synthesis conditions, the following parameters were determined: 27 g of pear peel was extracted with 360 mL of 50 vol% ethanol solution in water at 80 °C for 60 min, the Fe2+-extracts volume ratio was 1:1, and vacuum freeze drying was employed. The optimized YL-FeNPs formed particles of irregular shape with a size in the range of 40–80 nm. As the initial Cr(VI) concentration decreased and the adsorption temperature increased, its removal efficiency improved. After 2 h, a Cr(VI) removal efficiency of 96.8% was achieved for a solution with an initial Cr(VI) concentration of 12 mg/L. The adsorption of Cr(VI) conformed to pseudo-second-order kinetics and the Langmuir adsorption isotherm model. YL-FeNPs exhibited a maximum adsorption capacity of 43.99 mg/g at pH = 5 and 55 °C and demonstrated good adsorption performance in solutions with coexisting anions and real natural water. This research can support the recycling of pear peel waste and provide technical aspects for improving the synthesis efficiency of FeNPs.