Carbon coated ferrite precursor was prepared by one-pot hydrothermal method, which was calcined at 950 ℃ with N₂ protection to obtain carbon coated ferromagnet composite materials. The morphology and composition of the materials were analyzed by XRD, FT-IR and SEM, and the effects of reaction time, the ratio of starch and glucose on the morphology and IR extinction of the composite were studied. The IR extinction coefficients of materials in the range of 2.5-25 μm were measured and calculated by KBr method of FT-IR. The results show that the samples have good morphology and extinction performance, that were prepared under the conditions of reaction time of 20 h and 18 h and the ratio of starch and glucose of 9:3 and 6:10. In the range of 4-10 μm, the extinction coefficient of sample 5 and 7 is greater than 0.3 m²/g and the maximum is 0.37 m²/g.