Red phosphorus, as a metal free elemental photocatalyst, shows great potential applications for overall water splitting and environmental pollutants degradation. Facile fabrication of nano-sized and uniformly distributed phosphorus material is still challenging. Herein, we develop a facile approach to fabricate red phosphorus with particle size less than 10 nm through a hydrothermal and ultrasonic method. The hydrothermal and ultrasonic conditions were optimized. The red phosphorus sample hydrothermally treated at 200 degrees C for 12 h and then ultrasonically treated for 2 h at room temperature showed the best photocatalytic performance, which can effectively degrade Rhodamine B (RhB) and p-nitrophenol under visible light irradiation. The origin of the improved activity was attributed to the enhanced physical adsorption capacity, increasing active reaction sites and highly effective charge separation.