To improve the adsorption capacity of wheat biochar (BC) for arsenic (As), wheat stalks were selected as biomass to generate nano-sized goethite modified biochar (Goethite@BC) by co-precipitation. The adsorption capacities of BC, Goethite, and Goethite@BC for As(Ⅲ) were compared. The samples were analyzed by scanning electron microscopy (SEM) along with energy dispersive spectrometry (EDS), Brunauer-Emmett-Teller (BET), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. The results showed that the nano-goethite coating was uniformly attached to the surface of the BC and improved the surface area and total pore volume of the biochar. The adsorption of As(Ⅲ) by the three adsorbents was proved to fit well with the pseudo-second-order kinetic model and the Langmuir model. Compared to BC, the Goethite@BC increased the adsorption rate of As(Ⅲ) by 62.10 times, and the maximum adsorption capacity of Goethite@BC was 65.20 mg·g-1. The adsorption mechanism of Goethite@BC included non-specific adsorption (electrostatic attraction) and specific adsorption (coordination, complexation, ion exchange, etc.), and nano-goethite particles on the Goethite@BC surface played an important role in the adsorption of As. Goethite@BC has a good application prospects in the field of environmental remediation.