In this study, pure Ag4V2O7 was synthesized via hydrothermal method without surfactant at different temperatures (100°C, 120°C, and 140°C) and pH values (4 and 5) for the first time. Moreover, Ag4V2O7 nanoparticles with homogeneous size distribution about 200–300 nm can be obtained by adding polyvinylpyrrolidone to the synthesis system. Effects of hydrothermal synthesis conditions on photophysical properties and photocatalytic activity of Ag4V2O7 were investigated systematically. Ag4V2O7 sample prepared at 120°C and pH = 4 had the optimal photocatalytic activity among these samples, which almost completely degraded 10 ppm Rhodamine B within 3 h under visible light irradiation (420 nm < λ < 800 nm). The degradation products were measured by liquid chromatography–mass spectroscopy. The active species involved in the degradation process were analyzed by means of adding active species scavengers, electron spin resonance techniques, and photoelectrochemical experiments. A possible mechanism for photocatalytic degradation of organic pollutants on Ag4V2O7 photocatalyst was proposed and discussed preliminarily.