At present, the increasingly serious fluorine pollution in water is an enormous threat to human health, therefore, a three-dimensional porous magnesium aluminum hydrotalcite material doped with TiO2 and Al2O3 that can be used as defluorination material was synthesized by a green hydrothermal method and a series of comprehensive fluoride adsorption experiments were conducted in this study. The adsorption material has an ideal adsorption effect on fluoride due to its porous structure and various strong interactions with fluoride. The results of batch adsorption experiments indicate that the maximum adsorption capacity can reach up to 100.69 mg·g−1. Meanwhile, it can be applied in a wide pH range (3–10) and has strong resistance to the effect of coexisting anions. In addition, we explored the adsorption mechanism through DFT calculation, and found that electrostatic attraction, ion exchange, hydrogen bonding and chemisorption were the main adsorption mechanisms. Based on the above advantages, the adsorbent has a good application potential.