3-ketoacyl-acyl carrier protein (ACP) reductase is a vital enzyme in the biosynthesis of fatty acids in bacteria and plants. It assumes a critical role in the elongation process of fatty acids. The enzyme’s primary function is to catalyze the reduction of a 3-ketoacyl-ACP intermediate, forming a fully saturated acyl-ACP. This saturated acyl-ACP can subsequently elongate within the fatty acid synthesis pathway. This study successfully expressed and purified FnFabG from Fusobacterium nucleatum using Ni-NTA affinity and gel-filtration chromatography. The protein crystal was obtained and diffracted to a resolution of 2.7 Å. The preliminary crystallographic analysis suggested that FnFabG crystal belongs to the monoclinic space group P4₁2₁2 with a = b = 111.56 Å and c = 88.69 Å, α = β = γ = 90.00°. The asymmetric unit contained one molecule of FnFabG, giving a solvent content of 78.33%.