Several exfoliation methods including thermal treatment in air and hydrogen, ultrasonication, and chemical treatment with sodium borohydride were applied to modify the properties of bulk graphitic carbon nitride (g-CN). The prepared samples were characterized by X-ray diffraction, X-ray photoemission spectroscopy, Fourier transform infrared spectroscopy, UV-Vis diffuse reflectance spectroscope and N2 physisorption, and their photocatalytic performances were evaluated via the degradation of organic pollutants in aqueous solution. The results indicated that the exfoliation methods affect greatly on the physicochemical and photocatalytic properties of g-CN, and the optimum sample can be obtained by thermal treating in air (g-CN_A), showing 99.87% conversion at 40 min for the photocatalytic degradation of tetracycline hydrochloride, and the performance was preserved even after four cycles. The mechanism on the reaction intermediates with trapping experiments indicated that superoxide anion radicals (·O2-) are the main active species of the reaction.