Bi 2 O 3 nanosheet was synthesised using China rose petal as a biotemplate for the photodegradation of methylene blue under xenon lamp irradiation. The samples were characterised by thermogravimetric analysis-differential scanning calorimetric analysis, Fourier-transform infrared spectroscopy, nitrogen adsorption, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and ultraviolet-visible diffuse reflectance spectroscopy. The results revealed that the Bi 2 O 3 nanosheet with pure monoclinic phase was successfully synthesised by replication of the petal template with a thickness of about 100 nm, and showed the absorption thresholds wavelength of 480 nm. Moreover, the Bi 2 O 3 nanosheet exhibited 94.84% degradation efficiency of photodegradation of methylene blue in 180 min, which was much more active than that of the commercial α-Bi 2 O 3 due to its high specific surface area of 45.7 m 2 g −1 and wide band gap of 3.10 eV.