Exploring a simple method to prepare efficient photocatalyst is a very important technique for practical application. Herein, alpha-Bi2O3, beta-Bi2O3 and C/Bi/alpha-Bi2O3 were easily obtained by calcining bismuth citrate under different conditions. Especially, C/Bi/alpha-Bi2O3 obtained at 450 degrees C in nitrogen atmosphere exhibited superior photocatalytic activity for methyl orange (MO) and malachite green (MG) degradation under visible light irradiation, higher than beta-Bi2O3 and alpha-Bi2O3 calcined in air at 350 degrees C and above 450 degrees C, respectively. The presence of non-burned carbon in N-2 atmosphere benefits to complete transformation of beta-Bi2O3 into alpha-Bi2O3 at a annealing temperature low to 300 degrees C, as well as partial reduction of Bi2O3 into Bi nanoparticles. More importantly, the remaining carbon and metal Bi could enhance visible light absorption of alpha-Bi2O3, generate hot charge carriers and boost electron migration efficiency, which thus dramatically improve photocatalytic activity of alpha-Bi2O3. Furthermore, these bismuth oxides exhibit exceptionally strong adsorption ability for cationic dyes like MG and methyl violet (MV) with help of trace amount of ethylene diamine tetraacetic acid disodium salt (EDTA-2Na) and the maximum adsorption capacity for MG on alpha-Bi2O3 reached 312 mg/g. The as-prepared C/Bi/alpha-Bi2O3 also possesses good stability and recyclibility in photocatalysis and adsorption.