The GR4J model is a simple and practical conceptual hydrological model with remarkable characteristics in model principle andstructure. At present, application of this model is rather infrequent in China. In this paper, this model was applied to the daily runoff simulationof 19 different catchments over the Ganjiang River Basin during the period from 2003 to 2009. Results show that the Nash-Sutcliffe efficiencycoefficients for all the study areas exceeded 0.85 and the water volume relative error values were with ±10% during the calibration andvalidation periods. Thus, GR4J performed well in simulating daily runoff in the Ganjiang River Basin and it is promising in further applicationin other regions in China.