This study used bagasse as the raw material to produce biochar with high adsorption capacity by optimizing calcination conditions and introduced magnesium salt to prepare magnesium oxide-modified biochar. The prepared biochar was characterized using Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometry (EDS), X-ray Diffraction (XRD), Infrared Spectroscopy (FT-IR), and Specific Surface area and Porosity Analysis (BET). The adsorption rate on ferulic acid sucrose solution was used as the evaluation index to optimize four single factors: solution pH, adsorption temperature, adsorption time, and adsorbent dosage. Adsorption kinetics and thermodynamic models were applied to fit the experimental data and investigate adsorption behavior. The results showed that biochar produced at a carbonization temperature of 600 ℃ and a carbonization time of 2 h exhibited the best adsorption performance. SEM; EDS, XRD, FT-IR, and BET analyses confirmed successful magnesium loading and porosity, leading to enhanced adsorption capacity. The optimal conditions determined by single-factor experiments were pH 5.5, temperature 75 ℃, stirring time 120 min, and adsorbent dosage 150.00 mg. Under these conditions, the adsorption rate of modified biochar on ferulic acid sucrose solution reached 42.01%, markedly higher than that of unmodified biochar (29.01%) and macroporous resin (22.09%). Furthermore, the adsorption behavior was governed by multimolecular-layer chemical absorption. These findings suggest that magnesium oxide-modified biochar is a promising clarifying agent for sugar juice clarification.