Boron carbonitride (BCN) porous material is considered as an excellent adsorption material due to its high specific surface area and excellent chemical stability. In this paper, porous embryos were prepared by freeze-drying method and BCN porous material was synthesized by high-temperature solid-phase reaction method under NH3 atmosphere at different reaction temperatures with waste coconut shells, boric acid (H3BO3) and urea (CO(NH2)2) as raw materials. The results show that with the increase of reaction temperature, the pore size of BCN porous material gradually increases, and the average pore size is 2.1 nm when the reaction temperature is 950 ℃. The as-prepared BCN porous material is applied to adsorb malachite green (MG), an organic dye pollution in water, and its maximum adsorption capacity can reach 1 239.8 mg·g-1. After five cycles of regeneration, the average adsorption capacity is still as high as 1 138.6 mg·g-1, indicating that BCN porous material has excellent cyclic adsorption performance. Langmuir and Freundlich isothermal adsorption models, pseudo-first-order and pseudo-second-order adsorption kinetic models were used to study the relationship among concentration, adsorption time and equilibrium adsorption capacity. The results show that the adsorption of BCN porous material is consistent with the pseudo-second-order adsorption kinetic model, and the adsorption on MG belongs to the Langmuir isotherm adsorption of uniform surface monolayer molecules. The as-prepared BCN porous material exhibits excellent adsorption capacity and is expected to be a very promising adsorbent.