Within 40min, hexagonal boron nitride (h-BN) was rapidly synthesized via microwave heating without using catalyst and protective gas. Melamine and boric acid were used as raw materials, and carbon fiber was utilized as microwave absorber, respectively. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM) were used to characterize the structures and morphologies of the samples. Results indicated that the whisker-like h-BN with diameters of 200-500nm and lengths of 15-25m were successfully obtained. The specific surface area of the product was 510.941m(2)g(-1). The maximum adsorption capacity for methylene blue solution of the as-obtained h-BN was high up to similar to 230mgg(-1) at room temperature. The excellent adsorption performance of the samples may be attributed to the oxygen-containing functional groups and defects formed during the high-energy microwave irradiation.